Composite material and synthetic sleeper using the composite material

ABSTRACT

A composite material comprising a core layer comprising filler and synthetic resin and containing the filler having a weight 0.7 times or more the product of volume of the core layer and bulk density of the filler; and a surface layer comprising a thermosetting resin reinforced by long fibers extending parallel in a longitudinal direction thereof, the surface layer being laminated on the core layer to cover at least one surface of the core layer with respect to a thickness direction thereof.

This application is a United States national phase application ofInternational application PCT/JP99/06747 filed Dec. 1, 1999.

TECHNICAL FIELD

The present invention relates to a composite material and a syntheticcross tie using the composite material.

BACKGROUND ART

Fiber reinforced foam thermosetting resin molded goods, which resemblenative wood in appearance and show performances in physical propertiesequal to or more than native wood, are used as constitute materialsincluding building material, structural material, cross tie, and boardmaterial used for waterish places.

In general, the foam thermosetting resin molded goods of this type havea plate-like or bar-like molded main body which is formed by the foamthermosetting resin liquid being foamed and cured, as disclosed byJapanese Patent Publication No. Sho 52-2421 and Japanese Laid-openPatent Publication No. Hei 5-23947. In an interior of the main body,glass fibers having long fibers are paralleled in the longitudinaldirection as reinforced fibers and dispersed in generally parallel.

This conventional type of foam thermosetting resin molded goods have asufficient strength against a bending stress exerted in a directionorthogonal to the longitudinal direction in that the reinforced fibersare paralleled in the longitudinal direction and dispersed generallyparallel in the interior of the molded main body. However, they have thedisadvantage that for example, when nailed, they are easily cracked orfractured in a direction parallel to the reinforced fibers or thedisadvantage that they have a low unnailing strength.

In view of this, there was proposed a composite material in whichsurface layers, which comprises foam thermosetting resin and in whichreinforced fibers are paralleled in the longitudinal direction anddispersed in generally parallel, are laminated on both surfaces of acore layer comprising foam thermosetting resin in which not more than 50weight % of filler is dispersed (Cf. JP Laid-open Patent Publication No.Hei 5-138797).

In short, this composite material is made to have a sandwich structurein which the core layer of excellent in compressive strength issandwiched between the surface layers to thereby produce improvedcompression strength and nailing performance.

However, since this composite material has, as shown in FIG. 17, thestructure that thermosetting resin layer 300 exists between the filler200 of the core layer 100 and the filler 200, it has the disadvantagethat its compression strength and nailing performance are insufficientlyimproved.

Also, it suffers from the disadvantage that when the composite materialis deflected largely or bent repeatedly, the thermosetting resin layer300 is destroyed.

In the consideration of these circumstances, the present invention hasbeen made with the aim to provide a composite material capable tofurther improve its compression strength and nailing performance and asynthetic cross tie using the composite material.

DISCLOSURE OF THE INVENTION

To achieve this object, a composite material according to the presentinvention as set forth in claim 1 (hereinafter it is referred to as “thecomposite material of claim 1”) comprises a core layer comprising fillerand synthetic resin and containing the filler having a weight 0.7 timesor more the product of volume of the core layer and bulk density of thefiller; and a surface layer comprising a thermosetting resin reinforcedby long fibers extending parallel in a longitudinal direction thereof,the surface layer being laminated on the core layer to cover at leastone surface of the core layer with respect to a thickness directionthereof.

A composite material according to the present invention as set forth inclaim 2 (hereinafter it is referred to as “the composite material ofclaim 2”) comprises a core layer comprising filler and synthetic resinand containing the filler having a weight 0.7 times or more the productof volume of the core layer and bulk density of the filler; and asurface layer comprising a thermosetting resin including lightweightfiller reinforced by long fibers extending parallel in a longitudinaldirection thereof, the surface layer being laminated on the core layerto cover at least one surface of the core layer with respect to athickness direction thereof.

The composite material according to the present invention as set forthin claim 3 (hereinafter it is referred to as “the composite material ofclaim 3”) features that in the composite material of claim 1 or 2, thesurface layer has a density of 0.3 g/cm³ or more to 1.5 g/cm³ or less.

The composite material according to the present invention as set forthin claim 4 (hereinafter it is referred to as “the composite material ofclaim 4”) features that in the composite material of any one of claims 1through 3, it comprises a surface layer having a bending modulus of6,000 MPa or more and a bending strength of 100 MPa or more.

The composite material according to the present invention as set forthin claim 5 (hereinafter it is referred to as “the composite material ofclaim 5”) features that in the composite material of any one of claims 1through 4, the filler having an average particle size of 0.5 mm or moreis used.

The composite material according to the present invention as set forthin claim 6 (hereinafter it is referred to as “the composite material ofclaim 6”) features that in the composite material of any of claims 1through 5, the filler has two or more peak areas that constitute 8volume % or more on a particle size distribution curve plotting particlesize in abscissa and a volume ratio of filler per particle size to allfillers in ordinate and also has the size distribution that mostfrequent particle size values in the smaller peak area of 8 volume % ormore is 0.7 or less of most frequent particle size values in the largerpeak area of 8 volume % or more next to the smaller peak area.

The composite material according to the present invention as set forthin claim 7 (hereinafter it is referred to as “the composite material ofclaim 7”) features that in the composite material according to any ofclaims 1 through 6, thermosetting resin is used as the synthetic resinforming the core layer.

The composite material according to the present invention as set forthin claim 8 (hereinafter it is referred to as “the composite material ofclaim 8”) features that in the composite material of any of claims 1through 6, thermoplastic resin is used as the synthetic resin formingthe core layer.

The composite material according to the present invention as set forthin claim 9 (hereinafter it is referred to as “the composite material ofclaim 9”) features that in the composite material of any of claims 1through 7, thermosetting polyurethane resin foam of polyol equivalent of230 or more to 1,500 or less or thermosetting polyurethane resin foamhaving a density of 0.3 g/cm³ or more and polyol equivalent of 1,500 orless is used as the synthetic resin forming the core layer.

A composite material according to the present invention as set forth inclaim 10 (hereinafter it is referred to as “the composite material ofclaim 10”) comprises a core layer comprising filler and synthetic resinand a surface layer comprising synthetic resin foam and laminated on thecore layer to cover at least one surface of the core layer with respectto a thickness direction thereof, wherein a variation, curve of bendingstress of the core layer that varies with the bending and deflection hasa singular point at which slope of the tangent line decreasing graduallyfrom the point in time at which the bending is started increases againbefore becoming negative.

The composite material according to the present invention as set forthin claim 11 (hereinafter it is referred to as “the composite material ofclaim 11”) features that in the composite material of claim 10,thermosetting resin foam reinforced by long fibers extending parallel ina longitudinal direction thereof is used as the synthetic resin foam.

The composite material according to the present invention as set forthin claim 12 (hereinafter it is referred to as “the composite material ofclaim 12”) features that in the composite material of claim 10 or 11,the core layer has deflection of 0.8% or less at the singular point.

The composite material according to the present invention as set forthin claim 13 (hereinafter it is referred to as “the composite material ofclaim 13”) features that in the composite material of any of claim 10through 12, the core layer has the bending modulus of 800 MPa or morewhen further deflected from deflection at the singular point.

The composite material according to the present invention as set forthin claim 14 (hereinafter it is referred to as “the composite material ofclaim 14”) features that in the composite material of any of claim 1through 13, the core layer is formed by a plurality of core layerforming composition layers.

The composite material according to the present invention as set forthin claim 15 (hereinafter it is referred to as “the composite material ofclaim 15”) features that in the composite material of claim 14, one ofthe core layer forming composition layers is formed of thermosettingresin reinforced by long fibers extending parallel in a longitudinaldirection thereof or thermosetting resin including lightweight fillerreinforced by long fibers extending parallel in a longitudinal directionthereof.

A composite material according to the present invention as set forth inclaim 16 (hereinafter it is referred to as “the composite material ofclaim 16”) comprises a core layer comprising synthetic resin as a maincomponent and a surface layer comprising foam thermosetting resinreinforced by long fibers extending parallel in a longitudinal directionthereof or elastic synthetic resin reinforced by long fibers extendingparallel in a longitudinal direction thereof and laminated on the corelayer to cover both surfaces of the core layer with respect to athickness direction thereof, wherein the core layer and the surfacelayer have the relation that satisfies the equations of CSa≧½×CSb,Ea<Eb, and ESa≧½×ESb (where CSa represents yield strain in compressionof the core layer; CSb represents yield strain in compression of thesurface layer; Ea represents a tension elasticity modulus of the corelayer; Eb represents a tension elasticity modulus of the surface layer;ESa represents yield strain in tension of the core layer; and ESbrepresents yield strain in tension of the surface layer).

The composite material according to the present invention as set forthin claim 17 (hereinafter it is referred to as “the composite material ofclaim 17”) features that in the composite material of claim 16, itfollows that 0.005≦CSa, 50 MPa≦Ea, 0.005≦ESa, 0.01≦CSb, 5,000MPa≦Eb≦18,000 MPa, and 0.01≦ESb.

The composite material according to the present invention as set forthin claim 18 (hereinafter it is referred to as “the composite material ofclaim 18”) features that in the composite material of any of claims 1through 17, the core layer has a compression shear strength DBa of 5 MPaor more.

The composite material according to the present invention as set forthin claim 19 (hereinafter it is referred to as “the composite material ofclaim 19”) features that in the composite material of any of claims 1through 18, the core layer and the surface layer are integrally adhesivebonded to each other through an intermediate layer comprising non-foamthermosetting resin or low-power foam resin.

The composite material according to the present invention as set forthin claim 20 (hereinafter it is referred to as “the composite material ofclaim 20”) features that in the composite material of claim 19, anintermediate layer portion has the compression shear strength of 6 MPaor more, or the surface layer and the core layer both have thecompression shear strength of 6 MPa or more, when compressive force isapplied to the composite material in a direction parallel to the fiberextending direction of the long fibers of the surface layer so that abreaking surface can be formed in the intermediate layer portion, andwherein the composite material has the physical property that either thesurface layer or the core layer is first broken when the compressiveforce is applied to the composite material in the direction parallel tothe fiber extending direction of the long fibers of the surface layer sothat the breaking surface can be formed in the intermediate layerportion.

The composite material according to the present invention as set forthin claim 21 (hereinafter it is referred to as “the composite material ofclaim 21”) features that in the composite material of claim 19 or 20, aresin-impregnated sheet-like material is interposed in the intermediatelayer.

The composite material according to the present invention as set forthin claim 22 (hereinafter it is referred to as “the composite material ofclaim 22”) features that in the composite material of claims 1 through 7and claims 9 through 21, polyurethane resin foam is used as thesynthetic resin of the core layer and polyurethane resin foam is used asthe synthetic resin of the surface layer.

The composite material according to the present invention as set forthin claim 23 (hereinafter it is referred to as “the composite material ofclaim 23”) features that in the composite material of any of claims 1through 22, which has a total thickness of 100 mm or more and a ratiobetween a thickness of the core layer and a sum total of thickness ofthe surface layer covering the core layer in the thickness direction iswithin the range of 9/1 to 1/1.

The composite material according to the present invention as set forthin claim 24 (hereinafter it is referred to as “the composite material ofclaim 24”) features that in the composite material of claim 15 or 23,the core layer has at least two core layer forming composition layers(A) comprising filler and synthetic resin and at least one core layerforming composition layer (B) comprising thermosetting resin reinforcedby long fibers interposed between two core layer forming compositions(A),(A) of the at least two core layer forming composition layers (A)and extending parallel in a longitudinal direction of the compositematerial, and a ratio between a sum total of thickness of the core layerforming composition layer (A) and a sum total of thickness of the corelayer forming composition layer (B) is within the range of 95/5 to50/50.

The composite material according to the present invention as set forthin claim 25 (hereinafter it is referred to as “the composite material ofclaim 25”) features that in the composite material of any of claims 1through 24, the surface layer is laminated on the core layer to cover atleast two surfaces of the corer layer with respect to a thicknessdirection thereof; the composite material has a total thickness of 100mm or more with respect to a thickness direction thereof; a thickness ofthe surface layer on the side thereof on which a pulling force isexerted when the composite material is bent in the thickness directionis 5% or more to 25% or less of the total thickness; and the thicknessof the surface layer on the side thereof on which a compressive force isexerted is 1.5% or more to 15% or less of the total thickness.

The composite material according to the present invention as set forthin claim 26 (hereinafter it is referred to as “the composite material ofclaim 26”) features that in the composite material of any of claims 1through 25, the surface layer surrounds four surfaces of the core layerand constitutes 10 volume % or more to 65 volume % or less of the totalof the composite material.

A synthetic cross tie according to the present invention as set forth inclaim 27 (hereinafter it is referred to as “the cross tie of claim 27”)uses a composite material according to any of claims 1 through 26.

In the following, the constitution of the composite materials of therespective Claims will be described in detail.

While the synthetic resins which may be used for the core layer in thecomposite materials of claims 1 through 6 include thermosetting resinsas in the composite material of claim 7 and thermoplastic resin as inthe composite material of claim 8, the mixture of thermosetting resinand thermoplastic resin may be used.

While no particular limitation is imposed on the thermosetting resinsused for the core layer, the thermosetting resins which may be usedinclude the resins which are in liquid form or powder form beforereaction and are of foamable, including, for example, polyurethaneresin, phenol resin, unsaturated polyester resin, diallyl phthalateresin, vinyl ester resin, epoxy resin, urea resin, melamine resin,polyimide resin, polyamide-imide resin, acrylic resin, natural rubber,and synthetic rubber. These may be used in combination of two or more.

While no particular limitation is imposed on the thermoplastic resinsused for the core layer, the thermoplastic resins which may be usedinclude, for example, polystyrene, syndiotactic polystyrene,high-density polyethylene, low-density polyethylene, linear low-densitypolyethylene, polypropylene, rigid polyvinyl chloride, acrylic resin,ABS resin, aliphatic polyamide (nylon) resin, polyethyleneterephthalate, polybutylene terephthalate, polyoxymethylene,polycarbonate, polyarylate, polysulfone, polyether sulfone, polyetherether ketone, and polyphenylene sulfide, or copolymer thereof and blendthereof. Also, these may be of foamable.

Further, of these thermoplastic resins, crystalline resins havepreferably a melting point of 80° C. or more, or further preferably 120°C. or more. On the other hand, non-crystalline resins have preferably aglass transition point of 80° C. or more, or further preferably 100° C.or more. With the melting point and the glass transition point lowerthan these temperatures, there is the possibility that the bendingproperties and the heat resisting properties may reduce.

The filler having a coefficient. of thermal expansion approximating tothat of the long fibers for use in the surface material shouldpreferably be used.

While no particular limitation is imposed on the thermosetting resins.used for the surface layer in the composite materials of claims 1through 4, the thermosetting resins which may be used include the resinswhich are in liquid form or powder form before reaction and are offoamable, including, for example, polyurethane resin, phenol resin,unsaturated polyester resin, diallyl phthalate resin, vinyl ester resin,epoxy resin, urea resin, melamine resin, polyimide resin,polyamide-imide resin, and acrylic resin.

The foam thermosetting resins used for the surface layer include heatdecomposable foaming agents, such as azo compound and sodiumbicarbonate, solvent foaming agents, such as fleon, carbon deoxide andpentane, and foam thermosetting resin liquids including those from whichgas is formed as by-product in the reaction and curing. For example,rigid or semi-rigid polyurethane foam, phenol foam, low-power polyesterfoam can be cited.

Polyurethane foam, in particular, is preferably used in that it has arelatively high mechanical strength and can easily form closed cells,when foamed, and thus has excellent unabsorbent.

While no particular limitation is imposed on the lightweight filler usedin the surface layer in the composite material of claim 2, thelightweight fillers which may be used include, for example,powder/granular material, foam particle and hollow particle, such asglass hollow particle, silica balloon, fly ash balloon, shirasu balloon,porous glass, expanded shale, porous ceramics, perlite, pumice,vermiculite and synthetic resin. Synthetic resins which may be used asthe lightweight filler include the same thermosetting resin curingmaterial and rosslinked rubber as those used for the surface layer, andfurther include crystalline thermoplastic resin having a higher meltingpoint than a temperature at which the thermosetting resin is cured andnon-crystalline thermoplastic resin having a glass transition point.Those having closed cells are preferably used to reduce percentage ofabsorption of the composite material. The lightweight filler may besurface-treated with a silane coupling agent and the like.

In the composite material of claim 1 or 2, the surface layer haspreferably a density of 0.3 g/cm³ or more to 1.5 g/cm³ or less. Thereason therefor is that a too small density of the surface layer causesthe bending strength of the composite material to reduce, while on theother hand, a too large density of the surface layer causes thecomposite material to be easily cracked when nailed. The preferabledensity range varies depending on the intended use of the compositematerial. For example, for using the composite material to a railwaysleeper, the surface layer has further preferably a density of 0.6 g/cm³or more to 1.5 g/cm³ or less. For using the composite material toloading platform material or flooring material of a floating bridge, atrack and a boat, the surface layer has further preferably a density of0.3 g/cm³ or more to 0.8 g/cm³ or less.

In the composite material of claims 1 through 5, the long fiber is notlimited to any particular configuration, as far as it has the capabilityas the reinforced fiber. The long fibers which may be used include, forexample, mono-filament, fibril (a feathered fiber) chemical celluloseand weaving yarn. The materials thereof include organic materials, suchas glass, carbon and synthetic resin. Glass or carbon which produces alarge reinforcing effect is of preferable. These may be used singularlyor in combination of two or more.

While the percentage of the long fibers contained in the surface layeris not particularly limited, 5 volume % or more to 40 volume % or lessis of preferable. A less than 5 volume % of long fibers produce noreinforcing effects such as the bending strength. On the other hand, anexcess of 40 volume % of long fibers may produce a possible fracturerunning parallel to the fibers when the composite material is nailed.

When the thermosetting resin of the surface layer is foamable material,the resin density is preferably 0.2 g/cm³ or more. A less than 0.2 g/cm³resin density provides undesirable reduction of the bending strength. Noparticular upper limit is specified. An upper limit of a resin densityof the surface layer is substantially equal to that of the foamthermosetting resin that can substantially be produced.

In the composite material of claim 3, the surface layer preferablycontains 20 volume % or more to 50 volume % or less of lightweightfiller, in order to satisfy the above-noted proportion of the longfibers and the resin density of the thermosetting resin of foamablematerial. With a less than 20 volume % of lightweight filler, thesurface layer is easily cracked when nailed. On the other hand, with anexcess of 50 volume % of lightweight filler, the lightweight fillers arenot uniformly dispersed in the thermosetting resin, so that there is thepossibility that the physical properties, such as the bending strength,may be reduced.

In the composite material of claims 1 through 3, the bending modulus ofthe surface layer is preferably 6,000 MPa or more, as in the compositematerial of claim 4, further preferably 7,000 MPa or more, or stillfurther preferably 8,000 MPa or more. The reason is that a less than6,000 MPa bending modulus can cause reduction of the bending modulus ofthe entire composite material, so there is the possibility that, forexample, when used to railway sleepers, the composite materials maydeflect largely to easily cause deviation of a rail track. No particularupper limit of the bending modulus is specified. An upper limit of thebending modulus of the surface layer is substantially equal to that ofthe surface layer that can substantially be produced.

In the composite material of claims 1 through 3, the bending strength ofthe surface layer is preferably 100 MPa or more, as in the compositematerial of claim 4, or further preferably 120 MPa. The reason is thatwith a less than 100 MPa bending strength, there is the possibility thatwhen used to cross ties, the composite materials may easily reduce inlong-term bending durability.

The bending modulus and the bending strength are measured in accordancewith the method prescribed by JIS Z 2101. The bending load is applied toa test piece in a direction vertical to a longitudinal direction of thetest piece with the long-fiber extending direction as the longitudinaldirection.

In the composite material of claims 5 through 9, the same resins asthose used in the composite material of claims 1 through 4 can be usedas the resin for use in the surface layer.

In the composite material of claim 5, the average particle size of thefiller except the fibers is limited to 0.5 mm or more. The reason isthat with a less than 0.5 mm average particle size of the filler, whenthe filler having a weight 0.7 times or more the product of volume ofthe core layer and bulk density of the filler is tried to be contained,sufficient dispersion is not achieved in the mixing process of thefiller and the synthetic resin, so that the resin cannot adhere to thefiller uniformly and thus there is the possibility that satisfactoryphysical properties, such as the bending strength, cannot be obtained.The upper limit of the particle size of the filler is preferably made tobe substantially smaller than the thickness of the core layer. If thefiller having a diameter that will be substantially larger than thethickness of the core layer is used, then there is the possibility thatthe nailing property varies so largely, depending on the places to benailed, that the material cannot withstand continued use.

In the present invention, the particle size can be obtained by siftingwith a standard screen prescribed by JIS Z 8801. Combination of basicdimensions of meshes of typical screens for use in the sifting isselected from:

4.00 mm, 2.80 mm, 2.00 mm, 1.40 mm, 1.00 mm, 850 μm, 500 μm, 300 μm, 212μm, 106 μm, and 75 μm. Additional screens with different dimensions ofmeshes may properly be added.

The value of the particle size of the filler is expressed by the basicdimensions of meshes of the screens. The average particle size of thefiller is a value obtained by summing the products of volume ratios ofthe fillers remaining in the respective screens to the total fillersexcept the fibers and the values of particle sizes over all the screens.

While no particular limitation is imposed on the filler in the compositematerial of the present invention, the fillers which may be usedinclude, for example, amorphous powders, such as powder/granular rock,glass powder, quartz powder, calcium silicate, ground cement concrete,river sand, sea sand and silica sand, inorganic short fiber powders,such as wollastonite, inorganic powder/granular material having cells,such as expanded shale, pumice and glass foam, pulverized resins, suchas pulverized polyvinyl chloride, pulverized fiber-reinforced resin andpulverized fiber-reinforced foam polyurethane, inorganic powder having arelatively small particle size, such as calcium carbonate, fly ash,mica, talc, clay, alumina, vermiculite and sludge dry powder/granularmaterial, and granulated materials thereof previously bonded by resin.These may be used singularly or in combination of two or more.

The fibrous fillers which may be used include inorganic fibers, such asglass fiber, carbon fiber and boron fiber, and organic short fibers,such as vinylon fiber, polyester fiber, aliphatic polyamide fiber andaromatic polyamide.

Also, the above-noted inorganic fillers as surface-treated by silanecoupling agent may be used. When the polyurethane resin is used for theresin in the surface layer, silane coupling agent having a fimctionalgroup which reacts with an isocyanate group, such as a mercapto group,an amino group and an imino group, is preferably used.

In the composite material of claim 6, the filler used has two or morepeak areas that constitute 8 volume % or more on a particle sizedistribution curve plotting particle size in abscissa and a volume ratioof filler per particle size to all fillers in ordinate and also has thesize distribution that most frequent particle size values in the smallerpeak area of 8 volume % or more is 0.7 or less of most frequent particlesize values in the larger peak area of 8 volume % or more next to thesmaller peak area. The reason is that the mixture of fillers ofdifferent particle sizes can facilitate the mixture and impregnationinto the synthetic resin, especially the thermosetting resin, andfurther can facilitate increase of amount of filler added, tosignificantly enhance the laminating effect of the core layer and thesurface layer. In addition to this, the size distribution peaks at twoor more points, and as such can allow the resin to moderately filled inbetween the fillers. As a result of this, the composite material, whennailed, is resiliently compressed without the core layer being destroyedand the resilience provides improved nail holding ability and durabilityagainst the repeatedly applied unnailing force.

For the composite material of claim 5, the size distribution curve inthe composite material of claim 6 is obtained by plotting a volume ratioof the filler per particle size to all fillers except the fibersobtained in the same manner with respect to the each particle size. Thevolume ratio shows a volume ratio between the fillers screened withneighboring screens of basic dimensions.

The phrase of “the larger peak area of 8 volume % or more next to thesmaller peak area” is intended to mean that if a peak area of less than8 volume % exists between the large and small peak areas, such a peakarea of less than 8 volume % is not taken as the larger peak area of 8volume % or more next to the small peak area.

The volume % of the peak area is obtained as a percentage of an areasurrounded by the distribution curve extending between its boundariesintersecting the abscissa axis and the abscissa, in the case of itsboundaries not intersecting the abscissa, an area surrounded by thedistribution curve extending between minimum value points and theabscissa (in the case of using the minimum values, an area surrounded bythe distribution curve, the abscissa, and perpendicular lines droppedfrom the minimum value points to the abscissa) to a total area bounded.by the whole distribution curve and the abscissa, as shown in FIG. 18.

If the peak area has a tabletop peak extending parallel to the abscissa,a center of the parallel extending part is taken as the most frequentparticle size value.

In the composite material of claim 6, no particular limitation isimposed on the fillers providing larger values of the most frequentparticle sizes. The fillers include, for example, amorphous granularmaterials, such as granular rock, granular glass, calcium silicate,ground cement concrete, river sand, sea sand and silica sand, inorganicshort fiber powders, such as wollastonite, inorganic powder/granularmaterial having cells, such as expanded shale, pumice and glass foam,inorganic powder/granular materials having a relatively small particlesize, such as pulverized vinyl chloride, pulverized fiber-reinforcedresin, calcium carbonate and fly ash, and sludge dry powder/granularmaterial, and granulated materials thereof previously bonded by resin.On the other hand, no particular limitation is imposed on the fillersproviding smaller values of the most frequent particle sizes. Thepreferable fillers include, for example, powdered silica sand, quartz,mica, talc, clay and alumina and additionally include those belonging tosludge dry powder/granular material and inorganic powder/granularmaterial. These may be used singularly or in combination of two or more.Further, the above-noted inorganic fillers as surface-treated by silanecoupling agent may be used. When the polyurethane resin is used for theresin in the surface layer, silane coupling agent having an activehydrogen which reacts with an isocyanate group, such as a mercaptogroup, an amino group and an imino group, is preferably used.

In the composite material of claim 9, the polyol equivalent means avalue calculated from the following equation (1). The measuring methodis as follows. After the resin is hydrolyzed, amine originating fromisocyanate component is removed through ion exchange resin, alkalinecleaning and the like so that polyol component can be recovered, andthen the hydroxyl value of the recovered polyol component is measured.

Polyol equivalent=Molecular weight of KOH×1,000/Hydroxyl value of Polyol(mgKOH/g)  (1)

When a foam urethane resin having the polyol equivalent of 230 or moreto 1500 or less is used as the thermosetting resin forming the corelayer, the density of 0.25 g/cm³ or more to 0.6 g/cm³ is of preferable.

On the other hand, when a foam urethane resin having the density of 0.3g/cm³ or more and the polyol equivalent of 1,500 or less is used as thethermosetting resin forming the core layer, the polyol equivalent of 110or more to 1,200 or less is of preferable.

With the polyol equivalent of less than 110, the resin in the core layermay become too rigid, so that there is the possibility that flexibilityof the composite material itself may become insufficient. On the otherhand, with the polyol equivalent of more than 1,500, the resin in thecore layer may become too soft, so that there is the possibility thatthe nailing performance of the composite material may becomeinsufficient.

The density of polyurethane resin can be adjusted by adjusting a ratiobetween the fillers and the resin and foaming the polyurethane resin inbetween the fillers. The foaming is performed by use of foaming agent.The foaming agent may be selected properly for the resin used.

The foaming agents which may be used include, for example, physicalfoaming agents (volatile foaming agents), such as fleon, carbon deoxideand pentane, decomposition-type foaming agents, such as azo compound andsodium hydrogen carbonate, and reaction-type foaming agents, such ascarbon dioxide produced by reaction of isocyanate and water.

For polyurethane, carbon dioxide produced by reaction of isocyanate andwater should preferably be used because fleon can deplete the ozonelayer. Also, the foaming agent should be previously mixed with theresin.

In the composite material of claim 10, the flexibility can be calculatedfrom the following equation (2), using the deflection at a center ofspan=Δy, which corresponds to a permissible capacity at rated loadcenter distance in the evaluation of the bending strength. The bendingstrength is measured in accordance with the method prescribed by JIS Z2101.

Deflection (%)=6×(thickness of a test piece)×Δy/(span)²×100  (2)

The measurement may be made of the physical properties by cutting outthe core layer from the composite material or by producing the corelayer having the same construction.

The composite material is bent in the direction vertical to thelongitudinal direction of the test piece. The relation between thedeflection and the bending stress is shown in a graph plotting thedeflection in abscissa and the bending stress in ordinate.

In the composite material of claims 10 through 13, the singular pointmeans a non-differentiable bent back point, a point of inflection atwhich a curved line changes from concave to convex or conversely, andthe like.

In the composite materials of claims 10 and 11, the core layer hasdeflection of 0.8% or less, or preferably 0.7% or less, at the singularpoint, as in the composite material of claim 12. The reason is that withthe deflection of the core layer of more than 0.8% at the singularpoint, the composite material, when bent or compressed, may be brokenbefore the fillers are brought into contact with each other, so thatthere is the possibility of providing reduced strength.

In the composite materials of claims 10 through 12, it is preferablethat the core layer has the bending modulus of 800 MPa or more, orpreferably 950 MPa, when further deflected from deflection at thesingular point, as in the composite material of claim 13. The reason isthat the bending modulus of less than 800 MPa may reduce the effect thatthe fillers in the core layer are brought into contact to each otherwhen the composite material is bent or compressed, so that there is thepossibility of providing reduced strength.

In the case of the singular point being the bent back point, the bendingmodulus is the slope of the tangent line found from the large deflectiondirection.

In the composite materials of claims 10 through 13, either thermosettingresin which can be set under heat or at room temperature orthermoplastic resin which can be plasticized under heat may be used asthe synthetic resin used for the core layer.

The thermosetting resins which may be used include the resins which arein liquid form or powder form before reaction and are of foamable,including polyurethane resin, phenol resin, unsaturated polyester,diallyl phthalate resin, vinyl ester resin, epoxy resin, urea resin,melamine resin, polyimide resin, polyamide-imide resin, acrylic resin,natural rubber, and synthetic rubber. These may be used in combinationof two or more.

On the other hand, the thermoplastic resins which may be used includepolystyrene, syndiotactic polystyrene, high-density polyethylene,low-density polyethylene, linear low-density polyethylene,polypropylene, rigid polyvinyl chloride, acrylic resin, ABS resin,aliphatic polyamide resin, polyethylene terephthalate, polybutyleneterephthalate, polyoxymethylene, polycarbonate, polyarylate,polysulfone, polyether sulfone, polyether ether ketone, andpolyphenylene sulfide, or copolymer thereof and blend thereof. Also,these may be of foamable. Further, the thermosetting resin andthermoplastic resin may be used in combination.

In the composite materials of claims 10 through 13, no particularlimitation is imposed on the fillers. The fillers which may preferablyused include, for example, amorphous granular materials, such aspowder/granular rock, granular glass, calcium silicate, ground cementconcrete, river sand, sea sand and silica sand, inorganic short fiberpowders, such as wollastonite, inorganic powder/granular material havingcells, such as expanded shale, pumice and glass foam, inorganicpowder/granular materials having a relatively small particle size, suchas pulverized vinyl chloride, pulverized fiber-reinforced resin,pulverized fiber-reinforced rigid foam urethane, calcium carbonate andfly ash and hollow particles thereof, sludge dry powder/granularmaterial, mica, talc, clay, alumina, vermiculite, and glass shortfibers. In addition, inorganic fibers, such as carbon fiber and boronfiber, organic short fibers, such as vinylon fiber, polyester fiber,aliphatic polyamide fiber and aromatic polyamide, and granulatedmaterials thereof previously bonded by resin can be cited as thefillers. These may be used in combination of two or more. Further, theabove-noted inorganic fillers as surface-treated by silane couplingagent may be used. When the polyurethane resin is used for the resin inthe surface layer, silane coupling agent having an active hydrogen whichreacts with an isocyanate group, such as a mercapto group, an aminogroup and an imino group, is preferably used.

The sludge dry powder/granular materials include high-temperature drysolids content produced from a sludge treatment facility. The pulverizedfiber-reinforced resins include pulverized fiber-reinforced plastic(FRP) and pulverized fiber-reinforced rigid foam urethane. Further,fibrous ones include needle-like or shavings-like chips produced byscraping the fiber reinforced resin having unidirectionally alignedfibers in the fiber extending direction.

In the composite materials of claims 10 through 13, it is preferablethat the core layer contains the filler having a weight 0.7 times ormore the product (weight) of volume of the core layer and bulk densityof the filler.

With the amount of filer of less than 0.7 times the product (weight) ofvolume of the core layer and bulk density of the filler, thethermosetting resin layer is allowed to exist between the fillers andaccordingly the proportion of the fillers being not brought into directcontact with each other is increased. This makes it difficult to presentthe singular point and also may cause the compression strength and thenailing performance to be insufficient.

In the composite materials of claims 10 through 13, it is preferablethat the average density of the core layer is in the same range as inthe composite material of claim 1.

In the composite material of claim 10, either short fibers or longfibers may be used as the reinforced fiber used for the surface layer,though the long fibers are of preferable as in the composite material ofclaim 11. As far as the long fibers can reinforce the surface layer atleast in the longitudinal direction thereof, any of mono-filament,fibril synthetics and weaving yarn, and unidirectional reinforcing one,such as roving, bidirectional reinforcing one, such as a mat, andtridirectional reinforcing one, such as sewed mats, may selectively beused. These may be used singularly or in combination of two or more. Thesame reinforced fibers as those in the composite materials of claims 10and 11 may be used for the reinforced fibers of the surface layers ofthe composite materials of claims 12 and 13.

Either thermosetting resin which can be set under heat or at roomtemperature or thermoplastic resin which can be plasticized under heatmay be used as the synthetic resin used for the surface layer.

The thermosetting resins which may be used include the resins which arein liquid form or powder form before reaction and are of foamable,including polyurethane resin, phenol resin, unsaturated polyester,diallyl phthalate resin, vinyl ester resin, epoxy resin, urea resin,melamine resin, polyimide resin, polyamide-imide resin, acrylic resin,natural rubber, and synthetic rubber. These may be used in combinationof two or more.

On the other hand, the thermoplastic resins which may be used includepolystyrene, syndiotactic polystyrene, high-density polyethylene,low-density polyethylene, linear low-density polyethylene,polypropylene, rigid polyvinyl chloride, acrylic resin, ABS resin,aliphatic polyamide resin, polyethylene terephthalate, polybutyleneterephthalate, polyoxymethylene, polycarbonate, polyarylate,polysulfone, polyether sulfone, polyether ether ketone, andpolyphenylene sulfide, or copolymer thereof and blend thereof. Also,these may be of foamable.

Further, of these thermoplastic resins, crystalline resins havepreferably a melting point of 80° C. or more, or further preferably 120°C. or more. On the other hand, non-crystalline resins have preferably aglass transition point of 80° C. or more, or further preferably 100° C.or more. With the melting point and the glass transition point lowerthan these temperatures, the bending properties and the heat resistingproperties may reduce.

Further, the thermosetting resin and the thermoplastic resin may be usedin combination.

In the composite materials of claims 10 through 13, the foaming agentsused may selectively be used in accordance with the types of resins. Forexample, physical foaming agents, such as fleon, carbon deoxide andpentane, decomposition-type foaming agents, such as azo compound andsodium hydrogen carbonate, and reaction-type foaming agents, such ascarbon dioxide produced by reaction of isocyanate and water can becited.

For example, when polyurethane is used as the resin, carbon dioxideproduced by reaction of isocyanate and water should preferably be usedbecause fleon can deplete the ozone layer. These may be used singularlyor in combination of two or more. Also, the foaming agent shouldpreferably be previously mixed with the resin.

In the composite materials of claims 10 through 13, it is preferablethat the density of the surface layer is in the same range as in thecomposite material of claim 1, though no particular limitation isimposed thereon.

In the composite materials of claims 14 and 15, the same surface layeras those in the composite materials of claims 1 through 13 may be used.

When the composite material of the present invention is used forsynthetic cross ties, the long fibers extending parallel to thelongitudinal direction of the surface layer are preferably used.

In the composite materials of claims 14 and 15, it is preferable thatthe core layer forming material layers on the compression side thereofon which they are compressed when bent in the thickness direction are soconstituted that they contain the fillers having a weight 0.7 times ormore the product of volume of the core layer forming material layers andbulk density of the fillers so that the fillers in the core layerforming material layers, when compressed, can be brought into contactwith each other to provide high elasticity and high strength, while alsothe core layer forming material layers on the tension side are soconstituted that they are formed of the foam polyurethane resin havingthe polyol equivalent of 230 or more to 1,500 or less or the foampolyurethane resin having the density of 0.3 g/cm³ or more and thepolyol equivalent of 1,500 or less so that they can follow the expansionresulting from the deflection.

Also, it is preferable that the core layer forming material layers onthe tension side thereof contain elastic members, such as rubber chipsor springs, therein. The elastic members contained can provide vibrationabsorption to the composite material, while maintaining the high bendingmodulus by the surface layer and the core layer forming material layerson the compression side.

In the composite material of claim 15, the same as those of the surfacelayers of the composite materials of claims 1 through 13 may be used asthe core layer forming material layer (hereinafter, it is referred to as“the intermediate fiber reinforced layer”) which is interposed betweenthe core layer forming layer comprising filler and synthetic resin(hereinafter it is referred to as “the filler containing layer”) and thefiller containing layer and is formed of foam thermosetting resinreinforced by the long fibers extending parallel in the longitudinaldirection.

In the composite materials of claims 14 and 15, it is necessary that thecore layer forming material layers bordering on each other are bondedtogether. If those layers are not bonded adequately, there is thepossibility that the peel may be caused in the interface therebetween tocause the destruction of the entire composite material.

While no particular limitation is imposed on the bonding method, thebonding methods include, for example, the method of simultaneouslymolding the mutually bordering core layer forming material layers, themethod of adhesive bonding the molded core layer material layers to eachother by use of epoxy adhesive or urethane adhesive and the method ofmolding additional core layer forming material layer on the molded corelayer forming material layer.

In the composite material of claim 16, it is necessary that the corelayer and the surface layer have the relation that satisfies theequations of CSa≧½×CSb, Ea<Eb, and ESa≧½×ESb (where CSa represents yieldstrain in compression of the core layer; CSb represents yield strain incompression load of the surface layer; Ea represents a tensionelasticity modulus of the core layer; Eb represents a tension elasticitymodulus of the surface layer; ESa represents tensile yield strain of thecore layer; and ESb represents yield strain in tension of the surfacelayer). The reason is that if that relation is not satisfied, theperformance (bending) of the fiber reinforced surface layer is notbrought out, so that the composite material is not allowed to have theperformance (bending) equivalent to or more than the material comprisingonly the thermosetting resin reinforced by the long fibers extendingparallel in the longitudinal direction as in the surface layer or thethermosetting resin including the lightweight fillers reinforced by thelong fibers extending parallel in the longitudinal direction.Specifically, as shown in FIG. 11, even when the core layer is on theside (upper side in FIG. 11) on which compression is generated by a loadapplied to cause the longitudinal bending along the fiber extendingdirection of the surface layer, if the relation of CSa≧½×CSb issatisfied, the compression strength is improved. Also, even when thesurface layer is on the side (lower side in FIG. 11) on which tensionforce is generated, if the relation of Ea<Eb and ESa≧½×ESb is satisfied,the improvement of the bending strength can be expected.

In the composite material of claim 16, it is preferable that it followsthat 0.005≦CSa, 50 MPa≦Ea, 0.005≦ESa, 0.01≦CSb, 5,000 MPa≦Eb≦18,000 MPa,and 0.01≦ESb, as in the composite material of claim 17. The reason is asfollows.

In the core layer, the yield strain in compression CSa of 0.005 or morecan provide reinforced compression property of the surface layer. Thetension elasticity modulus Ea of 50 or more and the tensile yield strainESa of 0.005 or more can produce the effect of following the deflectionof the surface layer, to produce the composite material havingperformance (bending) equivalent to that of a single material of thesurface layer and durability against a repeated load equivalent to thatof the single material of the surface layer.

In the composite material of claims 16 and 17, it is preferable that thecompression modulus of elasticity Ca of the core layer in thelongitudinal direction is 300 MPa or more to 12,000 MPa or less and thecompression modulus of elasticity Cb of the surface layer is 2,000 MPaor more to 8,000 MPa or less, in that Ea and Eb are well balanced tofurther improve the durability.

Further, the composite material having the compression modulus ofelasticity Cb of the surface layer of 2,000 MPa or more to 8,000 MPa orless, the Eb of 5,000 MPa or more to 18,000 MPa or less and the ESb of0.01 or more can provide further sufficient strength as the structuralmember resembling the woods.

In the composite materials of claims 16 and 17, no particular limitationis imposed on the foam thermosetting resin forming the surface layer.For example, rigid or semi-rigid polyurethane foam, phenol foam,low-power foam polyester foam can be cited as those foam thermosettingresins, including the heat decomposable foaming agents, the solventfoaming agents, such as fleon, and the foam thermosetting resin liquidsincluding those from which gas is formed as by-product in the reactionand curing.

Polyurethane foam, in particular, is preferably used in that it has arelatively high mechanical strength and can easily form closed cells,when foamed, and thus has excellent unabsorbent.

On the other hand, while no particular limitation is imposed on theelastic synthetic resin forming the surface layer, the elastic syntheticresins include a resin belonging to the category of rubber, such aselastomer, flexible PVC and plastic polyvinyl alcohol. Resins havingcomparatively low elasticity, such as Polyolefin resin and high-impactABS, are also included, as far as they have a specified elasticity.

In the composite material of claims 16 and 17, the long fiber used inthe surface layer is not limited to any particular configuration, as faras it has the capability as the reinforced fiber. The same long fibersas those used for the surface layers of claims 1 through 15 may be used.

While the percentage of the long fibers contained in the surface layeris not particularly limited, 5 volume % or more to 40 volume % or lessis of preferable. A less than 5 volume % of long fibers produce noreinforcing effects such as the bending strength. On the other hand, anexcess of 40 volume % of long fibers may produce a possible fracturerunning parallel to the fibers when the composite material is nailed.

In the composite materials of claims 16 and 17, no particular limitationis imposed on the core layer. While the core layer is in general formedby the mixture of the fillers in the synthetic resin, it may be formedby two or more filler containing layers being laminated as in claims 14and 15 or by the intermediate finer-reinforced layer being interposedbetween the filler containing layer and the filler containing layer.

In the composite materials of claims 16 and 17, while no particularlimitation is imposed on the synthetic resin which is a main componentof the core layer or of the filler containing layer, the thermosettingresin or the thermoplastic resin may be used as that synthetic resin.

The thermosetting resins which may be used include the resins which arein liquid form or powder form before reaction and are of foamable,including, for example, polyurethane resin, phenol resin, unsaturatedpolyester resin, diallyl phthalate resin, vinyl ester resin, epoxyresin, urea resin, melamine resin, polyimide resin, polyamide-imideresin, acrylic resin, natural rubber, and synthetic rubber. These may beused in combination of two or more.

On the other hand, the thermoplastic resins which may be used includepolystyrene, syndiotactic polystyrene, high-density polyethylene,low-density polyethylene, linear low-density polyethylene,polypropylene, rigid polyvinyl chloride, acrylic resin, ABS resin,aliphatic polyamide resin, polyethylene terephthalate, polybutyleneterephthalate, polyoxymethylene, polycarbonate, polyarylate,polysulfone, polyether sulfone, polyether ether ketone, andpolyphenylene sulfide, or copolymer thereof and blend thereof. Also,these may be of foamable.

Further, of these thermoplastic resins, crystalline resins havepreferably a melting point of 80° C. or more, or further preferably 120°C. or more. On the other hand, non-crystalline resins have preferably aglass transition point of 80° C. or more, or further preferably 100° C.or more. With the melting point and the glass transition point lowerthan these temperatures, there is the possibility that the bendingproperties and the heat resisting properties may reduce.

Further, the thermosetting resin and the thermoplastic resin may be usedin combination.

For use of the foamable synthetic resin, those having the closed cellsare preferable to prevent water absorbing property.

The same fillers as those used for the core layer in the compositematerials of claims 1 through 15 may be used.

The same as the one used in the surface layer may be used as theintermediate fiber-reinforced layer.

In the composite materials of claims 1 through 17, it is preferable thatthe core layer has a compression shear strength of 5 MPa or more, as inthe composite material of claim 18. The reason is as follows.

If the compression shear strength DBa of the core layer is less than 5MPa or more, then the composite material cannot be allowed to have thebending strength equivalent to the material comprising only thethermosetting resin reinforced by the long fibers extending parallel inthe longitudinal direction as in the surface layer or the thermosettingresin including the lightweight fillers reinforced by the long fibersextending parallel in the longitudinal direction. As a result, there isthe possibility that the shear failure may be caused by the bending.

To obtain the compression shear strength DBa of the core layer of 5 MPaor more, it is preferable to treat the fillers with silane couplingagent or add the short fibers, pulverized fiber reinforced plastics,pulverized fiber reinforced rigid foam urethane, or fibrous onesincluding needle-like or shavings-like chips produced by scraping thefiber reinforced resin having unidirectionally aligned fibers in thefiber extending direction.

When the inorganic filler is used, the specific gravity of 0.5 or moreis of preferable. Preferably, the inorganic filler having the specificgravity of 0.5-1.5 in all fillers is 50 volume % or less of the totalcore layer.

Further, in the composite materials of claims 16 through 18, in the caseof possible occurrence of friction shearing in the surface, it ispreferable that at least two longitudinal surfaces of the core layer aresurrounded by the surface layer and/or the volume of the core layer is50% or more to less than 65% of the total volume of the compositematerial. The composite material thus constituted can provide animproved bending strength, as compared with the one comprising thesingle material of the surface layer, and is of advantageous inreduction of the material cost.

In the composite materials of claims 1 through 18, no particularlimitation is imposed on the production method. The composite materialmay be produced by either a batch process or a continuous process.

For reference's sake, an example of the batch production process is theprocess disclosed, for example, by Japanese Laid-open Patent PublicationNo. Hei 5-138797, in which after material preformed to form the corelayer and material preformed to form the surface layer are preformed andthen are set in casting molds, a mixture of the long fibers and thethermosetting resin, or a mixture of the filler and the thermosettingresin, or molding material thereof, which is to form the surface layeror the core layer, is filled in a casting mold before the preformedmaterial is cured, and then the thermosetting resin is set by heating.

On the other hand, an example of the continuous process is as follows. Anumber of long fibers to be the reinforced fibers are aligned parallelwith predetermined interval while they are traveled in one direction.Then, a foam thermosetting resin liquid is sprayed from over the groupof long fibers as aligned parallel on the travelling way. Thereafter,the foam thermosetting resin liquid thus sprayed is impregnated inbetween the fibers forming the respective long fibers.

Then, an extrusion shaping die is placed to confront a center part ofthe group of long fibers impregnated with the foam thermosetting resinliquid, and the mixture of the filler and thermosetting resin to formthe core layer is shaped to enclose the core layer by the group of longfibers while it is continuously extruded from the extrusion shaping die.Thereafter, they are continuously fed into a cylindrical molding passageto thermally set the foam thermosetting resin liquid in the moldingpassage, so as to form the core layer and the surface layersimultaneously.

As an alternative method thereto, the following method may by taken. Themixture of the filler and foam thermosetting resin to form the corelayer is fed in between the groups of two-tiered long fibers impregnatedwith the foam thermosetting resin liquid and then is pressed by endlessbelts and the like to be shaped into a specified section form enclosedby the group of long fibers. Thereafter, the layer thus shaped iscontinuously fed in the uncured condition or after foamed and thermallyset in the cylindrical molding passage. It is then continuously fed intothe cylindrical molding passage as it stands or after its surface isground, for example, by sanding, so that the foam thermosetting resinliquid is foamed and thermally set in the molding passage, so as to formthe core layer and the surface layer simultaneously or sequentially.

In the composite material of claim 19, the same synthetic resin, foamsynthetic resin, filler and long fiber as those used in claims 1 through18 may be used for the core layer and the surface layer.

In the composite material in claim 19, no particular limitation isimposed on the non-foam thermosetting resin and low-power foam resinused for the intermediate layer, as far as they have the adhesionproperties for allowing the surface layer and the core layer to adhereto each other. For example, polyurethane resin, epoxy resin, phenolresin, unsaturated polyester resin, urea resin, melamine resin,polyimide resin, polyamide-imide resin, acrylic resin, natural rubber,and synthetic rubber can be cited as the examples. If necessary,catalyst, foam stabilizer, foam assistant, filler, reinforcing shortfiber, coloring agent, ultraviolet absorbent, antioxidant, crosslinkingagent, stabilization agent, plasticizer, fire retardant, etc. may beadded (always excepting foaming agent). For reference's purpose, in thecase where polyurethane resins are used for the surface layer and thecore layer, the same polyurethane resin should preferably be used forobtaining high adhesion property.

In use of the polyurethane resin, even if no foaming agent such as wateris added, the polyurethane resin reacts with moisture in the air ormoisture from the surface layer or core layer to form some foaming, butsuch degree of foaming is of negligible.

Further, the intermediate layer is formed between the core layer and thesurface layer in order to integrate the core layer and the surfacelayer. No particular limitation is imposed on the thickness of theintermediate layer. If improvement is desired of the physicalproperties, such as the bending elasticity and the unnailing strength,then the non-foam thermosetting resin or low density foam resin of highelasticity modulus may be formed on the core layer to a largerthickness.

In the composite material of claim 20, the intermediate layer providedbetween the surface layer and the core layer is limited to 6.0 MPa ormore in the compression shear strength when compressive force is appliedto the composite material in a direction parallel to the fiber extendingdirection of the long fibers of the surface layer. Preferably, theintermediate layer has the compression shear strength of 7.0 MPa ormore, or further preferably 7.5 MPa or more. The compression shearstrength can be measured in accordance with the shearing test methodprescribed by JIS Z 2101.

The reason why the shear strength of the intermediate layer with respectto the fiber extending direction of the long fibers of the surface layeris limited to 6.0 MPa or more is as follows. With the shear strength ofthe intermediate layer of less than 6 MPa, the durability against therepeated bending is reduced, which tends to destruction in theintermediate layer in the form of destruction. The destruction of theintermediate layer in the form of destruction diffuses progressivelyover the destruction surface since the point of time of destruction, andthe reduction of strength makes rapid progress. As a result of this,this composite material can no longer be used for e.g. structuralmaterial and cross ties which require high elasticity, bending strengthand durability against the repeated fatigue.

No particular limitation is imposed on the method of providing the shearstrength of the intermediate layer of 6 MPa or more. For example, themethod of interposing a high-strength and high-elasticity resin, such asepoxy resin, between the surface layer and the core layer; the method ofmaking the resin density of the intermediate layer 1.1 times or more ofthe resin density of the surface layer and core layer when the shearstrength of the surface layer with respect to the fiber extendingdirection of the long fibers and the shear strength of the core layerare 6 MPa or more; and the method of arranging a resin impregnatedsheet-like material in the intermediate layer, as in the compositematerial of claim 21, can be cited as the examples.

The methods of making the density of the resin between the surface layerand the core layer higher than the density of resin of the surface layerand core layer include, for example, the method of applying epoxy resinor foam urethane resin or non-foam resin to the surface of the corelayer or the intermediate layer when the multi-layered material isproduced.

In the composite material of claim 21, the resin impregnated sheet-likematerial is the one that is impregnated with non-foam thermosettingresin or low-power foam resin and is used for the convenience sake toprovide the intermediate layer between the core layer and the surfacelayer. No particular limitation is imposed on the resin impregnatedsheet-like material, as far as it can be impregnated with non-foamthermosetting resin or low-power foam resin. For enhancing high strengthof the intermediate layer in itself, a high strength sheet-like materialmay be used.

No particular limitation is imposed on the resin impregnated sheet-likematerial, as far as it can be impregnated with non-foam thermosettingresin liquid or low-density foam resin liquid. The resin impregnatedsheet-like materials which may be used include, for example, non-wovenfabric comprising inorganic glass fibers or synthetic resin fibers (e.g.polyester non-woven fabric (SUPAN BONDO E 1050 available from ASAHICHEMICAL INDUSTRIAL CO., LTD. and vinylon non-woven fabric (e.g. BINIRONSUPAN REESU available from KURARAY CO., LTD.) and woven fabric. Inaddition, a porous sheet, having a number of holes, of a synthetic resinsheet, paper and metal fiber cloth may be used.

When the shear strength of the core layer is 6 MPa or the shear strengthof the surface layer is 6 MPa with respect to the fiber extendingdirection, the resin impregnated sheet-like material can allow theintermediate layer to be 6 MPa or more in the compression shear strengthwith respect to the direction parallel to the fiber extending directionby the density of the resin between the surface layer and the resinimpregnated sheet-like material and the density of the resin between thecore layer and the resin impregnated sheet-like material being made tobe 1.1 times or more of the density of the resin of the core layer andsurface layer.

When polyurethane resin is used as the resin of the core layer andsurface layer and the intermediate layer is interposed between the corelayer and the surface layer, the rein impregnated sheet-like material,of which raw material has a chemical/physical affinity for the resin ofthe core layer and surface layer, such as vinylon fiber or glass fibersubjected to the silane coupling treatment, and has excellent adhesionproperties, can allow the density of the resin between the surface layerand the sheet-like material and the density of the resin between thecore layer and the sheet-like material to be 1.05 times or more of thedensity of resin of the core layer and surface layer, for example whenthe shear strength of the core layer is 6 MPa or the shear strength ofthe surface layer is 6 MPa with respect to the fiber extendingdirection.

In the composite materials of claims 1 through 7 and claims 9 through21, it is preferable that the foam polyurethane resin is used as thesynthetic resin of the core layer and the synthetic resin of the surfacelayer, as in the composite material of claim 22.

The reason why the foam polyurethane resin is used for the core layer isthat it has a relatively high mechanical strength and is capable to formclosed cells easily when foamed, and excellent unabsorbent.

The foam polyurethane resins which may widely be used include known foampolyurethane resins obtained by the reaction with polyol andpolyisocyanate.

The polyols, having at least two hydroxyl groups at the molecular endthereof, include, for example, polyether polyol, such as polypropyleneoxide, polyethylene oxide and polytetramethylene glycol, and copolymersthereof, polyester polyols, such as polycondensate of aliphaticdicarboxylic acid, such as adipic acid, and glycol having not more than12 carbons, such as ethylene glycol, propylene glycol, butylene glycoland hexamethylene glycol, polyester polyol which is polycondensate ofhydroxycarboxylic acid, such as poly ε-caprolactone, and copolymerthereof, and polymer polyols which are graft copolymers of the polyolsand polymer of monomer having vinyl group. These may be used singularlyor in combination of two or more. The polyisocyanates which may be usedhave at least two isocyanate groups and include, for example,hydrogenated materials of 4,4′-methylene-diphenyl-diisocyanate,2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, isophoronediisocyanate, hexamethylene diisocyanate, and4,4′-methylene-diphenyl-diisocyanate, apocytes thereof, and apocytes ofisomers thereof. These may be used singularly or in combination of twoor more. In terms of safety, reactivity and convenience in handling, themixture of 4,4′-methylene-diphenyl-diisocyanate and apocyte of isomerthereof (hereinafter it is referred to as “the polymeric MDI”) is ofpreferable.

Examples of foaming agents used in the reaction are heat decomposablefoaming agents, pneumatogen, such as fleon, and water. Further,by-products, such as decomposed gas, produced in the reaction of theheat decomposable foaming agents may be used. Since fleon can depletethe ozone layer, carbon dioxide produced by reaction of isocyanate andwater should preferably be used. Also, the foaming agent should bepreviously mixed with the resin.

If necessary, catalyst, foam stabilizer, foam assistant, filler,reinforcing short fiber, coloring agent, ultraviolet absorbent,antioxidant, crosslinking agent, stabilization agent, plasticizer, fireretardant, etc. may be added to the foam urethane resin.

While no particular limitation is imposed on the catalyst, for exampleorganotin catalyst such as dibutyltin dilaurate, amine catalyst, andtemperature sensitive catalyst may be used.

The composite materials of claims 19 through 22 may be produced byeither a batch process or a continuous process.

Preferably, the curing timing of the respective layers should be in mostpossible exact with each other. This seems to be because this canprovide increased bonding force to contribute to improvement ofinterfacial strength if chemical bonds are formed between respectivelayers.

For reference's sake, reference is given to the batch production. Forexample, material preformed to form the core layer and materialpreformed to form the surface layer are preformed, first, and then areset in casting molds. In this process, the resin impregnated sheet-likematerial in which non-foam thermosetting resin was impregnated inadvance is rested on a surface of the thus-set preformed material on theside thereof on which the core layer and the surface layer arelaminated. Before the preformed material is cured, the mixture of longfiber and foam synthetic resin which is to form the surface layer, orthe mixture of filler and synthetic resin which is to form the corelayer, or an additional preformed material which is to form the surfacelayer or the core layer, is filled in a casting mold and then thesynthetic resin of the core layer and the surface layer and the non-foamthermosetting resin is cured by heating.

Referring now to the continuous process, for example, a number of longfibers which are to be the reinforced fibers are aligned parallel withpredetermined interval while they are traveled in one direction in twovertical levels. Then, a foam polyurethane resin liquid is sprayed fromover the groups of long fibers which were aligned parallel in twovertical levels on the travelling way, so that the sprayed foampolyurethane resin liquid is impregnated in between the fibers formingthe respective long fibers.

Further, in the state in which the resin impregnated sheet-like materialin which non-foam thermosetting resin liquid or low-power foam resinliquid was impregnated in advance is arranged between the groups oftwo-tiered long fibers impregnated with the foam thermosetting resinliquid, the mixture of the filler and foam thermosetting resin to formthe core layer is fed into and shaped by endless belts and the like, sothat they are shaped into a specified section form enclosed by the groupof long fibers and then are continuously fed in the as-uncuredcondition. Thereafter, they are continuously fed into a cylindricalmolding passage so that the foam thermosetting resin liquid can befoamed and thermally set in the molding passage, so as to form the corelayer, the surface layer and the intermediate layer simultaneously.

The composite material of claim 23 has a total thickness of 100 mm ormore and a ratio between a thickness of the core layer and a sum totalof thickness of the surface layer covering the core layer in thethickness direction is within the range of 9/1 to 1/1. The reason forthis requirement is that with the ratio of more than 9/1, the bendingstrength becomes insufficient, while on the other hand, with the ratioof less than 1/1, there is the possibility that either of thecompression strength and the nail holding performance resulting from theaddition of the fillers may not be satisfied.

In the composite material of claim 24, the core layer has at least twocore layer forming composition layers (A) comprising filler andsynthetic resin and at least one core layer forming composition layer(B) comprising thermosetting resin reinforced by long fibers interposedbetween two core layer forming compositions (A),(A) of the at least twocore layer forming composition layers (A) and extending parallel in alongitudinal direction of the composite material, and a ratio between asum total of thickness of the core layer forming composition layer (A)and a sum total of thickness of the core layer forming composition layer(B) is within the range of 95/5 to 50/50. The reason for thisrequirement is that with the ratio of more than 95/5, the nail holdingperformance of the core layer forming composition layer (B) which is theintermediate fiber-reinforced layer is reduced, while on the other hand,with the ratio of less than 50/50, there is the possibility thatcompression elasticity limit may be reduced.

In the composite material of claim 25, the surface layer is laminated onthe core layer to cover at least two surfaces of the core layer withrespect to a thickness direction thereof; the composite material has atotal thickness of 100 mm or more with respect to a thickness directionthereof; and a thickness of the surface layer on the side thereof onwhich a pulling force is exerted when the composite material is bent inthe thickness direction is 5% or more to 25% or less of the totalthickness and the thickness of the surface layer on the side thereof onwhich a compressive force is exerted is 1.5% or more to 15% or less ofthe total thickness. The reason is as follows.

When the thickness of the surface layer on the side thereof on which apulling force is exerted is too small, a sufficient bending strength maynot be presented. On the other hand, when the thickness of the surfacelayer on the side thereof on which the pulling is exerted is too large,the effect of reduction of material cost resulting from the provision ofthe core layer may be reduced. When the thickness of the surface layeron the side thereof on which a compressive force is exerted is toosmall, the core layer may be buckled due to a deformation, thereby, asufficient bending strength may not be presented. On the other hand,when the thickness of the surface layer on the side thereof on which thecompressive force is exerted is too large, the effect of reduction ofmaterial cost resulting from the provision of the core layer may bereduced.

In the composite material of claim 26, the surface layer surrounds foursurfaces of the core layer and constitutes 10 volume % or more to 65volume % or less of the total of the composite material. The reason forthis requirement is that with less than 10 volume %, the bendingstrength becomes insufficient, while on the other hand, with more than65 volume %, there is the possibility that either of the compressionstrength and the nail holding performance resulting from the addition ofthe fillers may not be satisfied.

The composite material of the present invention is suitable forstructural material. It can suitably be used as a substitution of woodand also for intended uses for weight reduction of concrete products,such as lids used in a water treatment plant, pressure bearing boardsused in the slop or equivalent places, sheathings for use in the ShieldEarth Retaining Wall method (hereinafter it is referred to as “the SEWconstruction method”) and cross ties as cited in claim 27.

It is to be noted that the SEW construction method is the constructionmethod in which a high strength and high durability wall is incorporatedin an earth retaining wall at a part thereof through which a shieldmachine passes so that the shield machine can directly cut that part ofthe wall to travel through it from a starting point to a terminal end,without any need for the cutting of the wall circularly by humans andmachines.

In the composite material and cross tie of the present invention, thesurface layer and the core layer may be provided, at their exposedsides, with a decoration layer, a weatherproof layer, and a waterprooflayer, if required.

While no particular limitation is imposed on the weatherproof layer, forexample a coating film formed by the application of weatherproof paintcan be cited as the weatherproof layer.

While no particular limitation is imposed on the waterproof layer, itmay be formed of a waterproof sheet and a waterproof board, made ofrubber, synthetic resin, metal sheet or combination thereof, and acoating film formed by the application of a non-immersible paint and theequivalent formed by the application or impregnation of water-repellentmaterial of oily material such as paraffin and petroleum jelly.

While the composite material of the present invention has an excellentnail holing performance, the nail holding performance may be furtherenhanced by forming prepared holes in nailing points, inpouring adhesivein the prepared holes, and then striking the nails therein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment of a composite material according to thepresent invention, showing a longitudinal sectional view thereof;

FIG. 2 is a variation curve of bending stress of the composite materialof FIG. 1;

FIG. 3 is a schematic diagram schematically showing a production unitfor the composite material of FIG. 1;

FIG. 4 is a schematic diagram of an enlarged sectional view of a corelayer of the composite material of FIG. 1;

FIG. 5 shows a second embodiment of the composite material according tothe present invention, showing a longitudinal sectional view thereof;

FIG. 6 shows a third embodiment of the composite material according tothe present invention, showing a longitudinal sectional view thereof;

FIG. 7 shows a fourth embodiment of the composite material according tothe present invention, showing a longitudinal sectional view thereof;

FIG. 8 shows a fifth embodiment of the composite material according tothe present invention, showing a longitudinal sectional view thereof;

FIG. 9 shows a sixth embodiment of the composite material according tothe present invention, showing a longitudinal sectional view thereof;

FIG. 10 shows a seventh embodiment of the composite material accordingto the present invention, schematically showing a perspective viewthereof;

FIG. 11 is an illustration for explaining a developing mechanism ofbending strength of the composite material;

FIG. 12 is a perspective view of a eighth embodiment of the compositematerial according to the present invention;

FIG. 13 is an illustration schematically showing a vertical productionline for use in producing the composite material of FIG. 12;

FIG. 14 is a sectional view of the composite material produced inReference Example 1;

FIG. 15 is a sectional view of the composite material produced inReference Example 2;

FIG. 16 is an illustration for explaining the way of a shearing test;

FIG. 17 is a schematic diagram of an enlarged sectional view of a corelayer of a conventional composite material; and

FIG. 18 is an illustration for explaining the way of finding a volumepercent of a peak area from a particle size distribution curve offiller.

BEST MODE FOR CARRYING OUT THE INVENTION

The detailed description on the embodiments of the present inventionwill be given with reference to the accompanying drawings.

Referring to FIG. 1, there is shown the 1st embodiment of a compositematerial according to the present invention.

As shown in FIG. 1, the composite material 1 a comprises a core layer 2a and a surface layer 3 a.

The core layer 2 a comprises filler 22 and thermosetting resin 21,contains the filler 22 having a weight 0.7 times or more the product ofvolume of the core layer and bulk density of the filler and has adensity of 0.3 g/cm³ or more to 2.3 g/cm³ or less.

The filler 22 is formed of at least one powder/granular materialselected from the group consisting of inorganic powder/granularmaterial, sludge dry powder/granular material and pulverizedfiber-reinforced resin.

As shown in FIG. 2, when the bending stress of the core layer 2 a thatvaries with variation of the deflection is plotted, a variation curvehaving a singular point P is plotted, at which point the slope of thetangent line T decreasing gradually from the point in time at which thebending is started increases again before becoming negative. The corelayer 2 a has the deflection of 0.8% or less at the singular point Pand, besides, has the bending modulus of 800 MPa or more when deflectedfurther from the deflection at the singular point.

The surface layer 3 a is arranged to surround the core layer 2 a fromaround it so as to be integral with the core layer 2 a and is formed offoam thermosetting resin whose long fibers 5 are aligned in generallyparallel in the longitudinal direction.

The surface layer 3 a constitutes 10 volume % or more to less than 65volume % of the total volume.

Next, the detailed description on the producing process of the compositematerial 1 a using a production unit shown in FIG. 3 will be given.

As shown in FIG. 3, the production unit 4 comprises a discharge machine41, an impregnating device 42, a continuous kneader 43, a shaping die44, a molding passage 45 and a take-off mechanism 46.

The discharge machine 41 is designed to continuously discharge foamthermosetting resin liquid 59 produced by the mixture of raw material ofthermosetting resin fed from a raw material tank (not shown) and sprayit over the long fibers 55 which are paralleled while passing throughthe molding passage 45 and are continuously taken off to the takeoffmechanism 46 side.

The impregnating device 42 is provided with an impregnating plate 42 aand an impregnating base (not shown) to receive the impregnating plate42 a. The group of long fibers 55 over which the foam thermosettingresin liquid 59 was sprayed is kneaded between the impregnating base andthe impregnating plate 42 a so that the foam thermosetting resin liquid59 can be uniformly impregnated in between the fibers.

The continuous kneader 43 is designed to mix the foam thermosettingresin liquid for forming the core layer 2 a and the filler to therebyproduce a mixed raw material and also continuously feed the mixed rawmaterial to the shaping die 44.

The shaping die 44 is designed to continuously shape the mixed rawmaterial fed from the continuous kneader 43 into a specified shape andalso feed the shaped material to a center part of the group of longfibers 55 on the way between the impregnating device 42 and the moldingpassage 45 as a shaped material 58 for use in forming the core layer.

The molding passage 45 is formed by combining four endless belts 45 a(only two of them are shown in the diagram) which are driven forrotation in the same direction by driving means and has a rectangularshape in section. It also has a heating device, though not shown, tofoam the foam thermosetting resin liquid 59 impregnated in the longfibers 5 continuously fed into the molding passage 45 and the foamthermosetting resin liquid in the shaped material 58 and cure them, tothereby produce the composite material 1 a having the core layer 2 a andthe surface layer 3 a having a section form as shown in FIG. 1. Thecomposite material thus produced is continuously fed through the moldingpassage.

The take-off mechanism 46 is designed to take off the composite material1 a at a regular speed.

In the composite material 1 a thus produced, the surface layer 3 a thatis formed in the state in which the long fibers 5 are aligned parallelin the longitudinal direction in the thermosetting resin. Thus, thecomposite material is easily nailed by a nail and the like and also isexcellent in bending strength exerted in the longitudinal direction.

Also, since the core layer 2 a comprises the filler 22 and thethermosetting resin 21 and since it contains the filler 22 having aweight 0.7 times or more the product of volume of the core layer andbulk density of the filler and has a density of 0.3 g/cm³ or more to 2.3g/cm³ or less, the fillers 22 are adhesive bonded with each otherthrough the thermosetting resin in the state in which the fillers areput in contact with each other, as shown in FIG. 4.

Therefore, the core layer 2 a is small in deformation againstcompression and also is dependent on the surface layer 3 a, so that itwill never be below the compression proportional limit of the surfacelayer 3 a. Accordingly, the composite material has excellent compressionstrength on the whole and also has improved unnailing performance by thefiller 22 of the core layer 2 a. In other words, since the filler 22 isdensely packed, the resistance to the unnailing is increased by thefiller 22 and the thermosetting resin 21 and thus the unnailing strengthis improved.

Further, since inorganic powder/granular material, sludge drypowder/granular material and pulverized fiber-reinforced resin are usedas the filler 22, the coefficient of thermal expansion of the filler isabout 1/10 of that of the thermosetting resin. Due to this, thecoefficient of thermal expansion of the core layer 2 a comes near thatof the surface layer 3 a reinforced by the glass fibers. Consequently,even when environmental temperature varies largely, little deformationis produced in an interface between the surface layer and the corelayer, thus providing a high reliability of long-term layer-to-layeradhesion properties.

In addition, since the surface layer 3 a comprises foam thermosettingresin reinforced by the long fibers aligned parallel in the longitudinaldirection and constitutes 10 volume % or more to less than 65 volume %of the total volume, the composite material has a sufficient property inbending strength and also is resistance to the crack or fracture whennailed.

Besides, the variation curve of the bending stress of the core layer 2 ahas the singular point P at which the slope of the tangent linedecreasing gradually from the point in time at which the bending isstarted increases again before becoming negative and also the deflectionof the core layer is 0.8% or less at the singular point P. Furthermore,the core layer has the bending modulus of 800 MPa or more when deflectedfurther from the deflection at the singular point. Due to this, thebending strength is improved. The occurrence of the singular pointprovides the result that when the composite material is bent orcompressed, the fillers are brought into full contact with each other toproduce improved strength.

Referring to FIG. 5, there is shown the 2nd embodiment of the compositematerial according to the present invention.

As shown in FIG. 5, the composite material 1 b is formed with a corelayer 2 b sandwiched between the surface layers 3 b located on top andbottom surfaces of the core layer.

The core layer 2 b is formed of filler contained in a proportion ofexcess of 50 volume % to 95 volume % or less, and foam polyurethaneresin of polyol equivalent of not less than 230 to not more than 1,500or foam polyurethane resin of density of not less than 0.3 g/cm³ andpolyol equivalent of not more than 1,500.

The surface layers 3 b are formed of foam thermosetting resin reinforcedby the long fibers aligned parallel in the longitudinal direction.

The composite material 1 b is produced by the following processes:First, a mixture of the filler and the foam polyurethane resin liquid isfilled in a casting mold to form it into a core layer shape. Then, priorto the curing of the shaped material, the shaped material is sandwichedin between a thermosetting resin foam sheet reinforced by fibers thatbecome the surface layer and then is cured in this state in the castingmold by heating.

In this composite material 1 b, since the core layer 2 b includes thefillers contained in a proportion of excess of 50 volume % to 95 volume% or less, as mentioned above, the fillers 22 are adhesive bonded witheach other via the foam polyurethane resin in the state in which thefillers are put in contact with each other, as is the case with thecomposite material 1 a mentioned above.

Therefore, the core layer 2 b is small in deformation againstcompression and also is dependent on the surface layer 3 b, so that itwill never be below the compression proportional limit of the surfacelayer 3 b. Accordingly, the composite material has excellent compressionstrength on the whole and also has improved unnailing performance by thefiller of the core layer 2 b. In other words, since the filler 22 isdensely packed, the resistance to the unnailing is increased by thefiller and the foam polyurethane resin and thus the unnailing strengthis increased.

Besides, since the foam polyurethane resin forming the core layer 2 bhas polyol equivalent of not less than 230 to not more than 1,500 or hasa density of not less than 0.3 g/cm³ and polyol equivalent of not morethan 1,500, the flexibility is also improved.

Hence, when the composite material is used as the cross tie and thelike, that will be able to easily absorb vibrations to reduce noise. Inaddition, since the core layer is resistant to destroying, if damageoriginates from deterioration, the damage will then be caused to thesurface layer and thus will be easily detectable.

Further, specific gravity of the composite material produced can beeasily adjusted by adjusting the specific gravity of fillers of the corelayer, such that the composite material can be used for various usesranging from weight saving use to weighted use.

Referring to FIG. 6, there is shown the 3rd embodiment of the compositematerial of the present invention.

As shown in FIG. 6, the composite material lc comprises a core layer 2 ccomprising two filler-containing layers 23, 24 as core layer formingcompositions and a surface layer 3 c arranged to surround the core layer2 c.

The filler-containing layers 23, 24 are formed of foam polyurethaneresin of polyol equivalent of not less than 230 to not more than 1,500or foam polyurethane resin of density of not less than 0.3 g/cm³ andpolyol equivalent of not more than 1,500, and material including thefiller having a weight 0.7 times or more the product of volume of thefiller-containing layers 23, 24 and bulk density of the filler.

The two filler-containing layers 23, 24 are different in compoundingratio of fillers from each other; are slightly different in physicalproperties from each other; and are adhesive bonded together in theinterface therebetween.

The surface layer 3 c is formed of foam thermosetting resin reinforcedby the long fibers aligned parallel in the longitudinal direction.

In the composite material 1 c, since the core layer 2 c is formed of twofiller-containing layers 23, 24 different in physical properties fromeach other, as mentioned above, the filler-containing layers 23, 24 andthe surface layer 3 c cooperate efficiently against the bending, toprovide improved strength and flexibility of the composite material.

Referring to FIG. 7, there is shown the 4th embodiment of the compositematerial of the present invention.

As shown in FIG. 7, the composite material 1 d is identical to theabove-mentioned composite material 1 c, except that a core layer 2 d isformed of two filler-containing layers 23, 24 different in physicalproperties from each other and an intermediate fiber-reinforced layer25.

The intermediate fiber-reinforced layer 25 is formed of foamthermosetting resin reinforced by the long fibers aligned parallel inthe longitudinal direction, as is the case with the surface layer 3 c,and is adhesive bonded to the upper and lower filler-containing layers23, 24 to be integral therewith.

In this composite material 1 d, since the intermediate fiber-reinforcedlayer 25 is provided between the filler-containing layer 23 and thefiller-containing layer 24, as mentioned above, the nail struck can bebound by the long fibers of the intermediate fiber-reinforced layer 25to provide an improved nail holding performance of the compositematerial.

Hence, the composite material can be used suitably for a cross tie (arailway sleeper, in particular), a pressure bearing board and a shieldearth retaining wall method (SEW) which require high bending strengthand bending modulus. Also, since the product size can be reduced forpurposes not requiring high bending strength and bending modulus, costreduction of material can be achieved.

Referring to FIG. 8, there is shown the 5th embodiment of the compositematerial of the present invention.

As shown in FIG. 8, the composite material 1 e is identical to theabove-mentioned composite material 1 d, except that a core layer 2 e isformed of two filler-containing layers 23, 23 identical to each otherand an intermediate fiber-reinforced layer 25.

Referring to FIG. 9, there is shown the 6th embodiment of the compositematerial of the present invention.

As shown in FIG. 9, the composite material 1 f is identical to theabove-mentioned composite materials 1 d, 1 e, except that a core layer 2f is formed of three filler-containing layers 23, 24, 26 different inphysical properties from each other and an intermediate fiber-reinforcedlayer 25.

Specifically, the intermediate fiber-reinforced layer 25 is providedbetween the filler-containing layer 24 and the fuler-containing layer 26and the filler-containing layer 23 and the filler-containing layer 24are directly adhesive bonded with each other.

Referring to FIG. 10, there is shown the 7th embodiment of the compositematerial of the present invention.

As shown in FIG. 10, the composite material 1 g comprises a core layer 2g containing synthetic resin as the main component and a surface layer 3g which comprises foam thermosetting resin reinforced by long fibersaligned parallel in the longitudinal direction or elastic syntheticresin reinforced by long fibers aligned parallel in the longitudinaldirection and which is arranged to surround the core layer 2 g.

The core layer 2 g and the surface layer 3 g have the relation thatsatisfies the equations of CSa≧½×CSb, Ea<Eb, and ESa≧½×ESb (where Carepresents a compression modulus of elasticity of the core layer in thelongitudinal direction; Cb represents a compression modulus ofelasticity of the surface layer in the longitudinal direction; CSarepresents yield strain in compression of the core layer; CSb representsyield strain in compression of the surface layer; Ea represents atension elasticity modulus of the core layer; Eb represents a tensionelasticity modulus of the surface layer; ESa represents yield strain intension of the core layer; and ESb represents yield strain in tension ofthe surface layer) and it follows from the equations that 300MPa≦Ca≦12,000 MPa, 0.005≦CSa, 50 MPa≦Ea, 0.005≦ESa, 2,000 MPa≦Cb≦8,000Mpa, 0.01≦CSb, 5,000 MPa≦Eb≦18,000 MPa, and 0.01≦ESb.

The core layer 2 g contains the filler having a weight 0.7 times or morethe product of volume of the core layer and bulk density of the fillerand has a shear strength DBa of 5 MPa or more.

The composite material 1 g thus constituted provides the results ofsuppressing destroy of the core layer and improving flexibility, inaddition to bending strength, compression proportional limit, nailingproperty and unnailing property. Hence, when the composite material isused as the cross tie and the like, that will easily absorb vibrationsto reduce noise.

Referring to FIG. 12, there is shown the 8th embodiment of a compositematerial according to the present invention.

As shown in FIG. 12, the composite material 1 h comprises a core layer 2h, an intermediate layer 7 h and a surface layer 3 h and has arectangular form in section.

The core layer 2 h comprises filler and foam polyurethane resin,contains the filler having a weight 0.7 times or more the product ofvolume of the core layer and bulk density of the filler and has adensity of 0.3 g/cm³ or more to 2.3 g/cm³ or less.

The filler is formed of at least one powder/granular material selectedfrom the group consisting of inorganic powder/granular material, sludgedry powder/granular material and fiber reinforcing resin pulverizedmaterial.

The surface layer 3 h is formed of foam polyurethane resin whose longfibers are aligned in generally parallel in the longitudinal direction.

The surface layer 3 h constitutes 10 volume % or more to 65 volume % orless of the total volume.

The intermediate layer 7 h is formed of polyurethane resin as non-foamthermosetting resin. The surface layer 3 h and the core layer 2 h areintegrated through the intermediate layer 7 h by adhesive bonding.

The intermediate layer 7 h includes a resin impregnated sheet-likematerial, though not shown, and has a shear strength of 6 MPa or morewhen it is compressed in a direction parallel to the fiber extendingdirection of the long fibers 5 of the surface layer 3 h.

Referring to FIG. 13, there is shown a vertical shaping line of oneexample of the production method of the composite material 1 h.

With reference to FIG. 13, the production method will be described underthe following respective processes.

(1) Feeding and Paralleling of Long fibers:

In FIG. 13, long fibers 81 are fed from straightening vanes (not shown)from four directions corresponding to the respective sides of theproduct obtained (only two directions are shown in the diagram), so thatlong fiber bundles 82 which are drawn with tension while being alignedgenerally parallel with given intervals are made to travel in onedirection.

(2) Impregnation, Positioning and Introduction of Roving:

Thereafter, foam polyurethane resin in solution form is trickled down onthe long fiber bundles 82 from foam polyurethane resin tanks 83 locatedover the long fiber bundles 82 in travel, for adhesion thereto. Then,the long fiber bundles 82 to which the foam polyurethane resin adheredare fed to impregnating plates 84. The impregnating plates 84 are movedin reciprocation in a direction orthogonal to the travelling directionof the long fiber bundles to knead the long fiber bundles 82, so as toimpregnate the foam polyurethane resin in between the long fibersforming the long fiber bundles 82.

Then, the resin impregnated long fiber bundles 85 corresponding inposition to the four sides are positioned in inlets of movable molds 86on their respective sides.

Guides (not shown) may then be used for making change of or making fineadjustment of the travelling direction.

Then, the resin impregnated long fiber bundles 85 are each introducedinto a movable molds 86 by a driving force applied from a take-offmechanism 88, while contacting with four sides of the movable mold 86.It is noted here that the movable mold 86 defines a closed space inwhich endless belts 86 a are arranged in four directions (only twodirections in the diagram).

(3) Introduction of Resin Impregnated Sheet-like Material:

Non-foam thermosetting resin liquid is trickled down on resinimpregnated sheet-like material 87 from a mixing head 89, first, andthen the resin impregnated sheet-like material 87 is allowed to passthrough impregnating rolls 90 to impregnate the non-foam thermosettingresin in the sheet-like material 87. The resin impregnated sheet-likematerial 87′ thus impregnated is introduced into the movable mold 86 sothat it can be located between the core layer 2 h and the surface layer3 h in the composite material 1 h produced.

(4) Casting of Filler:

Then, foam polyurethane resin composition 92 in which fillers such assilica sand is added and mixed is cast and dropped from a mixing device91 into a space surrounded by the long fiber bundles 85 which arepositioned in the four sides of the interior of the movable mold 86 andare impregnated with the polyurethane resin liquid and the resinimpregnated sheet-like material 87 which are positioned at the inside ofthe long fiber bundles 85 and are impregnated with the non-foamthermosetting resin. The mixing device 91 is provided with an inlet 91 afor the foam polyurethane resin liquid, an inlet 91 b form the filler,and a main body (a mixing portion).

(5) Shaping of Laminate:

The resin liquid containing therein the above-mentioned filler, the longfiber bundles 85 impregnated with the surrounding resin liquid, and theresin impregnated sheet-like material 87′ impregnated with the non-foamthermosetting resin, such as non-foam polyurethane resin, are moveddownward in synchronization with each other by the endless belts 86 aforming the movable mold 86.

In the course of the movement, the filler containing resin, the longfiber bundles 85 impregnated with the surrounding resin liquid, and theresin impregnated sheet-like material 87 impregnated with the non-foamthermosetting resin are, first, subjected to heat from the endless belts86 a heated by a heating/cooling segment 86 c to generate a foaming andcuring reaction to thereby produce a fiber reinforced resin laminate 1h′ in which the core layer 2 h, the surface layer 3 h and theintermediate layer 7 h provided therebetween are generally formed. Then,the fiber reinforced resin laminate 1 h′ is cooled down by the endlessbelts 86 a cooled by a lower heating/cooling segment 86 c.

(6) Cooling:

Then, the multi-tiered formation is got out of the movable mold 86 andfed to a cooling device 93. The multi-tiered formation is fully cooleddown by cooling rolls 93 a in the cooling device 93.

(7) Cutting:

Thereafter, after having passed through the take-off mechanism 88, thefiber reinforced resin laminate is cut to a desired length with acutting device 94 to obtain the composite material 1 h.

In this composite material 1 h, the surface layer 3 h and the core layer2 h are integrated through the intermediate layer 7 h by adhesivebonding, as aforementioned. Hence, this composite material can easily benailed and has an excellent bending strength in the longitudinaldirection, as is the case with the composite material 1 a, as well ascan suitably be used for structural material for use in e.g. ashield-use take-off/accession coffering wall for use in the SEWconstruction method.

The composite material like the composite material disclosed, forexample, by Japanese Laid-open Patent Publication No. Hei 5-138797,wherein the surface layers comprising thermosetting resin foam in whichreinforced long fibers are paralleled in the longitudinal direction tobe dispersed in generally parallel are laminated on surfaces of the corelayer comprising the thermosetting resin foam to which the filler wasadded, can be made with a large thickness with comparative ease.However, since both the core layer and the surface layer comprise thethermosetting resin foam, the interfacial strength is so low for theapplication to the SEW construction method that peeling can easily becaused in the interface and, for this reason, it was practicallydifficult for the composite material to be used for that constructionmethod.

In contrast to this, in the composite material 1 h, the surface layer 3h and the core layer 2 h are firmly integrated with each other throughthe intermediate layer 7 h by adhesive bonding, so that the problem ofthe peeling being caused in the interface is prevented. In other words,since the non-foam thermosetting resin layer exists in the interfacebetween the core layer and the surface layer, the composite material isof excellent in adhesion strength in the interface, in other words, ininterfacial strength.

This is presumably because the adhesion strength in the interface, inother words, the chemical bonding per unit area and the degree of anchorbonding in the interface are higher than those in the interface of thenon-foam layers being bonded to each other.

Besides, the intermediate layer 7 h has a shear strength of 6 MPa ormore when it is compressed in a direction parallel to the fiberextending direction of the long fibers 81 of the surface layer 3 h, sothat when the composite material is subjected to repeated bendingfatigue, the core layer or the surface layer is broken, rather than thein terminate layer. Hence, the spread of braking over the breakingsurface to cause a sharp strength reduction which occurs when theintermediate layer is broken is prevented. Accordingly, the compositematerial of the present invention can preferably be used for thepurposes requiring high elasticity, high bending strength and durabilityagainst the repeated bending fatigue, including structural materials,such as the shield-use take-off/accession coffering wall for use in theSEW construction method, and cross ties.

The composite material according to the present invention is not limitedto the above-illustrated embodiments. For example, while the productionunit 4 of the above-illustrated embodiment is so designed that the foamthermosetting resin liquid 59 is sprayed over the group of long fibers55 and then is impregnated therein with the impregnating device 42, thegroup of long fibers 55 may alternatively be immersed into the foamthermosetting resin liquid or may be made to pass through between tworolls with banks, to be impregnated with the foam thermosetting resinliquid.

Also, while the vertical production unit is used in the productionmethod of the composite material 1 h, a horizontal production unit mayalternatively be used.

EXAMPLES

In the following, the examples of the present invention will bedescribed in further detail.

Example 1

After a core layer having a section of a size of 190×100 mm comprisingthe foam thermosetting urethane resin liquid and the filler shown in thefollowing TABLE 1 was produced, the core layer was cast in the castingmold to produce a composite material having a section of a size of200×140 mm having a surface layer comprising the long fibers and thefoam thermosetting resin liquid shown in TABLE 1 and extending alongfour lengthwise surfaces.

The composite material produced showed that a ratio of the thickness ofthe core layer to the sum total of thickness of the surface layercovering the core layer with respect to the thickness direction was 2.5;that the thickness of the surface layer on the side thereof on which apulling force was exerted when the composite material was bent in thethickness direction represented 14% of the total thickness; and that thethickness of the surface layer on the side thereof on which acompressive force was exerted represented 14% of the total thickness.

In TABLE 1, the polyether polyol represents propylene oxide addedpolyether polyol (available from Sumitomo Bayer Urethane Ltd., SUMIPHEN1703, hydroxyl value of 380, polyol equivalent of 147) and the peakparticle diameter ratio represents a ratio of most frequent particlediameter values in adjoining peak areas of 8 volume % or more.

The particle diameter of the filler was adjusted with a screen as shownin TABLE 1. The proportion of the filler was obtained by dividing aweight of the filler in the core layer by (a volume of the core layer×abulk density of the filler). The densities on the following TABLE areexpressed in the units of g/cm³.

[Table 1]

Example 2

After a core layer having a section of a size of 190×160 mm comprisingthe foam thermosetting urethane resin liquid and the filler shown in thefollowing TABLE 2 was produced, the core layer was cast in the castingmold to produce a composite material having a section of a size of200×200 mm having a surface layer comprising the long fibers and thefoam thermosetting resin liquid shown in TABLE 1 and extending alongfour lengthwise surfaces.

The composite material produced showed that a ratio of the thickness ofthe core layer to the sum total of thickness of the surface layercovering the core layer with respect to the thickness direction was 4;that the thickness of the surface layer on the side thereof on which apulling force was exerted when the composite material was bent in thethickness direction represented 10% of the total thickness; and that thethickness of the surface layer on the side thereof on which acompressive force was exerted represented 10% of the total thickness.

In TABLE 2, the polyether polyol represents propylene oxide addedpolyether polyol (available from Mitsui Chemicals, Inc., MN-3050S,hydroxyl value of 56, polyol equivalent of 1,000) and the peak particlediameter ratio represents a ratio of most frequent particle diametervalues in adjoining peak areas of 8 volume % or more.

The particle diameter of the filler was adjusted with the screen asshown in TABLE 2.

[Table 2]

Example 3

After a core layer having a section of a size of 190×80 mm comprisingthe foam thermosetting urethane resin liquid and the filler shown in thefollowing TABLE 3 was produced, the core layer was cast in the castingmold to produce a composite material having a section of a size of200×120 mm having a surface layer comprising the long fibers and thefoam thermosetting resin liquid shown in TABLE 3 and extending alongfour lengthwise surfaces.

The composite material produced showed that a ratio of the thickness ofthe core layer to the sum total of thickness of the surface layercovering the core layer in the thickness direction was 2; that thethickness of the surface layer on the side thereof on which a pullingforce was exerted when the composite material was bent in the thicknessdirection represented 21% of the total thickness; and that the thicknessof the surface layer on the side thereof on which a compressive forcewas exerted represented 13% of the total thickness.

In TABLE 3, the polyether polyol represents a mixture of polyolequivalent of 270 produced by mixing 50 weight % of propylene oxideadded polyether polyol (available from Sumitomo Bayer Urethane Ltd.,SUMIPHEN 1703, hydroxyl value of 380) and 50 weight % of propylene oxideadded polyether polyol (available from Sumitomo Bayer Urethane Ltd.,SUMIPHEN 3900, hydroxyl value of 35).

The particle diameter of the filler was adjusted with the screen asshown in TABLE 3.

[Table 3]

Example 4

After a core layer having a section of a size of 190×100 mm comprisingthe foam thermosetting urethane resin liquid and the filler shown in thefollowing TABLE 4 was produced, the core layer was cast in the castingmold to produce a composite material having a section of a size of200×140 mm having a surface layer comprising the long fibers and thefoam thermosetting resin liquid shown in TABLE 4 and extending alongfour lengthwise surfaces.

The composite material produced showed that a ratio of the thickness ofthe core layer to the sum total of thickness of the surface layercovering the core layer in the thickness direction was 2.5; that thethickness of the surface layer on the side thereof on which a pullingforce was exerted when the composite material was bent in the thicknessdirection represented 14% of the total thickness; and that the thicknessof the surface layer on the side thereof on which a compressive forcewas exerted represented 14% of the total thickness.

In TABLE 4, the polyether polyol represents a mixture of polyolequivalent of 270 produced by mixing 50 weight % of propylene oxideadded polyether polyol (available from Sumitomo Bayer Urethane Ltd.,SUMIPHEN 1703, hydroxyl value of 380) and 50 weight % of propylene oxideadded polyether polyol (available from Slumitomo Bayer Urethane Ltd.,SUMIPHEN 3900, hydroxyl value of 35).

The particle diameter of the filler was adjusted with the screen asshown in TABLE 4.

[Table 4]

Example 5

After powder of polyethylene terephthalate resin and the filler shown inthe following TABLE 5 were mixed and dispersed, the mixture was used toproduce a core layer having a section of a size of 200×100 mm byhot-press molding. Thereafter, the core layer was cast in the castingmold to produce a composite material having a section of a size of200×140 mm having a surface layer comprising the long fibers,unsaturated polyester resin liquid of iso series and fly ash balloon(available from Japan Fillite Ltd.) shown in TABLE 5 and extending alongtwo upper and lower surfaces.

The composite material produced showed that a ratio of the thickness ofthe core layer to the sum total of thickness of the surface layercovering the core layer in the thickness direction was 2.5; that thethickness of the surface layer on the side thereof on which a pullingforce was exerted when the composite material was bent in the thicknessdirection represented 14% of the total thickness; and that the thicknessof the surface layer on the side thereof on which a compressive forcewas exerted represented 14% of the total thickness.

The particle diameter of the filler was adjusted with the screen asshown in TABLE 5.

[Table 5]

Comparative Example 1

Except that the core layer and the surface layer shown in the followingTABLE 6 were formed, the composite material was produced in the samemanner as in Example 1.

[Table 6]

Comparative Example 2

Except that the core layer and the surface layer shown in the followingTABLE 7 were formed, the composite material was produced in the samemanner as in Example 1.

[Table 7]

Comparative Example 3

Except that the core layer and the surface layer shown in the followingTABLE 8 were formed, the composite material was produced in the samemanner as in Example 1.

However, propylene oxide added polyether polyol (available from MitsuiChemicals, Inc., MN-300, hydroxyl value of 560, polyol equivalent of100) was used as the polyether polyol.

[Table 8]

Comparative Example 4

Except that the core layer and the surface layer shown in the followingTABLE 9 were formed, the composite material was produced in the samemanner as in Example 1.

However, propylene oxide added polyether polyol (available from SumitomoBayer Urethane Ltd., SUMIPHEN 3900, hydroxyl value of 35, polyolequivalent of 1,600) was used as the polyether polyol.

[Table 9]

The examinations were made of the bending strength, compressionproportional limit, nailing property and innailing property of thecomposite materials produced in Examples 1-5 and Comparative Examples1-4. The results are shown in TABLE 10. Also, the examination was madeof the flexibility in Examples 1-4 and Comparative Examples 3 and 4, andthe examination was also made of the repeated unnailing property inExamples 1-3 and Comparative Example 1. These examination results arealso shown in TABLE 10.

The bending strength and the compression proportional limit weremeasured in accordance with the method prescribed by JIS Z 2101.

As for the nailing property, prepared holes of φ17 mm and depth of 110mm were bored and then rail screw nails prescribed by JIS E 1109 werescrewed into the prepared holes. The composite materials which were notfractured by the boring, were tightened with 80 kN-m or less runningtorque, and were not cracked in their surfaces by the screw tighteningwere represented by ∘ and all other composite materials than those wererepresented by x.

As for the unnailing property, the screwed nails screwed in the nailingproperty tests were pulled out. Not less than 38 kN is represented by⊚⊚, Not less than 33 kN is represented by ⊚, Not less than 28 kN isrepresented by ∘, Not less than 23 kN is represented by Δ, and Less than23 kN is represented by x.

The repeated unnailing property was evaluated by the screw nailsscrewed-in in the unnailing property tests being unnailed repeatedlywith a maximum load of 20 kN and a sinusoidal wave of 3 Hz. Those inwhich no destroy was found at one million repeated unnailings wererepresented by ⊚, those in which the screw nails were uinnailed athundred thousand or more to less than one million repeated unnailingswere represented by ∘, and those in which the screw nails were unnailedat less than hundred thousand repeated unnailings were represented by x.

As for the flexibility:

It was calculated from the following equation, using the deflection at acenter of span=Δy, which corresponds to a permissible capacity at ratedload center distance in the evaluation of the bending strength.

Deflection (%)=6×(thickness of a test piece)×Δy/(span)²×100

[Table 10]

It is found from TABLE 10 that the composite materials of the presentinvention were excellent in bending strength, compressive property,nailing property and unnailing property.

Example 6

After the fillers were dispersed in the foam thermosetting resinsolution shown in the following TABLE 11, they were cast in the mold togenerate a foaming and curing reaction at 100° C. for 30 minutes andthereby a core layer having a rectangular section of a size of 200mm×100 mm was produced.

Then, 110 parts by weight of thermosetting foam urethane mixed solutionshown in TABLE 11 was sprayed over 110 parts by weight of long fibersshown in TABLE 11 so as to be impregnated in the long fibers.Thereafter, in the state of being aligned parallel in the longitudinaldirection of the core layer, the long fibers were made to extend withthickness of 20 mm (in the thickness direction) along upper and lowersurfaces of the core layer and also extend with thickness of 5 mm (inthe widthwise direction) along both lateral side surfaces of the corelayer. Thereafter, they were cast in the mold to be foamed and cured at80° C. for 30 minutes and thereby the composite material having asection of a size of 210 mm×140 mm was produced.

Used as the propylene oxide added polyether polyol in the foamthermosetting resin liquid of the core layer was SUMIPHEN 1703 availablefrom Sumitomo Bayer Urethane Ltd. (hydroxyl value of 380 and polyolequivalent of 147).

[Table 11]

Example 7

Except that the core layer and the surface layer shown in the followingTABLE 12 were formed, the composite material was produced in the samemanner as in Example 6.

Used as the propylene oxide added polyether polyol in the. foamthermosetting resin liquid of the core layer was a mixture of 50 weight% of SUMIPHEN 1703 available from Sumitomo Bayer Urethane Ltd. (hydroxylvalue of 380 and polyol equivalent of 147) and 50 weight % of SUMIPHEN3900 available from Sumitomo Bayer Urethane Ltd. (hydroxyl value of 35and polyol equivalent of 1,600).

[Table 12]

Comparative Example 5

Except that the core layer and the surface layer shown in the followingTABLE 13 were formed, the composite material was produced in the samemanner as in Example 6.

Used as the propylene oxide added polyether polyol in the foamthermosetting resin liquid of the core layer was SUMIPHEN 1703 availablefrom Sumitomo Bayer Urethane Ltd. (hydroxyl value of 380 and polyolequivalent of 147).

[Table 13]

Comparative Example 6

The molded material comprising only the longitudinally fiber reinforcedfoam resin with the same compounding as that of the surface layer ofExample 6 was produced.

The measurements were made of the compression proportional limit andnailing property of the composite materials or molded materials producedin Examples 6, 7 and Comparative Examples 5, 6. Also, the measurementswere made of the bending strength, bending modulus and deflection (%) atthe singular point of the composite materials produced in Examples 6, 7and Comparative Example 5 and the bending modulus of the same when thedeflection is increased from the singular point. The results are shownin TABLE 14.

It is to be noted that the bending modulus when the deflection isincreased was calculated from the slope of the tangent line at thesingular point found from the large deflection direction.

The bending strength, the bending modulus and the compressionproportional limit were measured in accordance with the methodprescribed by JIS Z 2101.

The deflection was calculated from the equation of Deflection(%)=6×(thickness of a test piece)×Δy/(span)²×100, using the deflectionat a center of span=Δy, which corresponds to a permissible capacity atrated load center distance in the evaluation of the bending strength.

The core layer and the composite material were bent in the directionorthogonal to the longitudinal direction of the test piece. As to thecomposite material, the alignment direction of the long fibers containedin the surface layer was taken as the longitudinal direction of the testpiece.

As for the unnailing property, after the prepared holes having adiameter of 17 mm and a depth of 110 mm were bored in the surface of thetest piece covered with the surface layer, the rail screw nailsprescribed by JIS E 1109 were driven 20 mm to their underhead fillets.Then, the unnailing resistance values were measured at a velocity of 10mm per minute. Not less than 23 kN is represented by Δ, Not less than 28kN is represented by ∘, Not less than 33 kN is represented by ⊚, andLess than 23 kN is represented by x.

[Table 14]

It will be understood from TABLE 14 that the composite material of thepresent invention thus constructed can produce excellent bending andcompression strength, improved compression properties, in particular, ascompared with the material comprising only the surface layer and no corelayer, and excellent unnailing properties and, hence, can be effectivelyused for synthetic woods, particularly for cross ties.

Example 8

The filler containing foam thermosetting resin liquid of the same kindas the one used for forming the core layer of Example 6 was cast in themold as a first filler-containing layer material, first, and then wasevened out. Thereafter, the filler containing foam thermosetting resinliquid of the same kind was cast in the mold as a secondfiller-containing layer material. Then, they were subjected to thefoaming and curing reaction at 100° C. for 30 minutes and thereby thecore layer was produced which comprises the first filler-containinglayer having a rectangular section of a size of 200 mm×100 mm and athickness of 50 mm and the second filler-containing layer having athickness of 50 mm which layers are laminated.

Then, the composite material, having the surface layer which extendswith thickness of 20 mm along upper and lower surfaces of the core layerand with thickness of 5 mm along both lateral side surfaces of the corelayer and is identical in constitution to that of Example 6 and having asection of a size of 210×140 mm, was cast-molded in the same manner asin Example 6.

Example 9

The filler-containing foam thermosetting resin liquid of the same kindas the one used for forming the core layer of Example 6 was cast in themold as a first filler-containing layer material, first, and then wassubjected to the foaming and curing reaction at 100° C. for 30 minutesto thereby produce a sheet material that is a first filler-containinglayer having a rectangular section of a size of 200 mm×50 mm.

Subsequently, a first intermediate material of a size of 210×75 mmhaving a long fiber reinforced layer extending with a thickness of 20 mmalong an upper surface of the sheet material, with a thickness of 5 mmalong a lower surface thereof, and with a thickness of 5 mm along bothlateral sides thereof was produced in the same conditions as those forthe surface layer of Example 6.

Then, the filler-containing foam thermosetting resin liquid of the samekind as the one used for forming the core layer of Example 2 was cast inthe mold as a second filler-containing layer material, first, and thenwas subjected to the foaming and curing reaction at 100° C. for 30minutes to thereby produce a sheet material that is a secondfiller-containing layer having a rectangular section of a size of 200mm×50 mm.

Subsequently, a second intermediate material of a size of 210×65 mmhaving a long fiber reinforced layer extending with a thickness of 5 mmalong an upper surface of the sheet material, with a thickness of 5 mmalong a lower surface thereof, and with a thickness of 5 mm along bothlateral sides thereof was produced in the same conditions as those forthe surface layer of Example 6.

Then, epoxy adhesive (ESURON 410 available from Sekisui Chemical Co.,Ltd.) was applied to a lower surface of the first intermediate materialthus produced and an upper surface of the second intermediate materialthus produced. Those surfaces were put in press-contact with each otherat room temperature for 24 hours to thereby produce a composite materialhaving an intermediate fiber-reinforced layer having a thickness of 10mm between the first filler-containing layer and the secondfiller-containing layer.

The examinations were made of the bending strength, bending modulus,unnailing property and deflection of the composite materials produced inExamples 8 and 9. The results are shown in TABLE 15, together with thoseof the composite material of Example 6.

As for the unnailing property, after the prepared holes having adiameter of 17 mm and a depth of 120 mm were bored in the surface of thetest piece covered with the surface layer, the rail screw nailsprescribed by JIS E 1109 were driven 20 mm to their underhead fillets.Then, the unnailing resistance values were measured at a velocity of 10mm per minute. Not less than 23 kN is represented by Δ, Not less than 28kN is represented by ∘, Not less than 33 kN is represented by ⊚, Notless than 38 kN is represented by ⊚⊚, Not less than 43 kN is representedby ⊚⊚⊚, and Less than 23 kN is represented by x.

[Table 15]

It will be understood from TABLE 15 that the composite material havingthe core layer formed by the lamination of a plurality of core layerforming composition layers provides an improved bending strength, ascompared with the composite material having the core layer of a singlelayer structure. Further, the core layer formed to have the intermediatefiber-reinforced layer between the filler-containing layer and thefiller-containing layer provides an improved unnailing property as well.

Example 10

As shown in TABLE 16, raw material of foam vinyl chloride resin in which0.05 parts by weight of ADCA (azodicarbonamide) as a foaming agent wascompounded in 100 parts by weight of vinyl chloride resin (PVC compoundavailable from Tokuyama Sekisui Co., Ltd.) was extruded to form asheet-like molded product having a section of a size of 160×100 mm thatforms the core layer.

The sheet-like molded product was surrounded by use of the long fibersand the foam thermosetting resin liquid shown in TABLE 16 and theproduction unit 4 shown in FIG. 3, to produce a composite material of asize of 200×140 mm in section having a surface layer around the corelayer having the section of the size of 160×100 mm.

[Table 16]

Example 11

A composite material having a section of a size of 200×140 mm, whichincludes the surface layer comprising the long fibers and the foamthermosetting resin liquid shown in TABLE 17 to surround the core layerhaving a section of a size of 160×100 mm comprising the foamthermosetting resin liquid and the filler shown in the following TABLE17, was produced with the production unit 4 shown in FIG. 3. The shapedmaterial extruded from the shaping die had a section of 160×100 mm.

[Table 17]

Example 12

A composite material having a section of a size of 200×140 mm, whichincludes the surface layer comprising the long fibers and the foamthermosetting resin liquid shown in TABLE 18 to surround the core layerhaving a section of a size of 160×100 mm comprising the foamthermosetting resin liquid and the filler shown in the following TABLE18, was produced with the production unit 4 shown in FIG. 3. The shapedmaterial extruded from the shaping die had a section of 160×100 mm.

[Table 18]

Comparative Example 7

A composite material having a section of a size of 200×140 mm andcomprising only the long fibers and foam thermosetting resin liquid usedfor the surface layer of Example 10 was produced.

Comparative Example 8

As shown in TABLE 19, after a mixture of 20 parts by weight ofresol-base phenol particles (BERU PAARU (Name of article) available fromKANEBO, LTD.) and 80 parts by weight of No. 5 silica sand was preheated,the mixture was hot-pressed at 200° C. with 20kg/cm² to thereby producea porous material that is the core layer having a section of a size of160×100 mm.

This porous material was surrounded by use of the long fibers and thefoam thermosetting resin liquid shown in TABLE 19 and the productionunit 4 shown in FIG. 3, to produce a composite material having a sectionof a size of 200×140 mm having a surface layer around the core layerhaving the section of the size of 160×100 mm.

[Table 19]

Comparative Example 9

As shown in TABLE 20, polystyrene resin (available from SUMITOMOCHEMICAL CO., LTD.) was extruded and foamed to produce a polystyrene lowpower foam that is the core layer having a section of a size of 160×100mm.

This foam was surrounded by use of the long fibers and the foamthermosetting resin liquid shown in TABLE 20 and the production unit 4shown in FIG. 3, to produce a composite material having a section of asize of 200×140 mm having a surface layer around the core layer havingthe section of the size of 160×100 mm.

[Table 20]

Comparative Example 10

Elastic urethane foam that is the core layer of 160×100 mm was producedby using urethane resin having the composition shown in TABLE 21.

This elastic urethane foam was surrounded by use of the long fibers andthe foam thermosetting resin liquid shown in TABLE 21 and the productionunit 4 shown in FIG. 3, to produce a composite material having a sectionof a size of 200×140 mm having a surface layer around the core layerhaving the section of the size of 160×100 mm.

[Table 21]

The examinations were made of Ca, Cb, CSa, CSb, Ea, Eb, ESa, ESb, DBa,bending strength, nailing property and unnailing property of thecomposite materials produced in Examples 10-12 and Comparative Examples7-10. The results are shown in TABLE 22.

[Table 22]

It will be clearly understood from TABLE 22 that the setting of CSa,CSb, Ea, Eb, ESa, ESb, and DBa to the constitution of the compositematerial of claims 10 and 11 enables the volume of the surface layer toreduce and achieves improvement in bending strength and improvement inflexibility as well as in compression proportional limit, nailingproperty and unnailing property.

Example 13

A composite material having a section of a size of 200×140 mm and alength of 2,020 mm and comprising a core layer having a section of asize of 180×100 mm shown in the following TABLE 23, an intermediatelayer comprising a non-foam urethane resin of a thickness of about 2 mmand polyester non-woven fabric (SUPAN BONDO E 1050 available from ASAHICHEMICAL INDUSTRIAL CO., LTD.) as a resin impregnated sheet-likematerial, and a surface layer shown in TABLE 23 was produced with thevertical production line shown in FIG. 13.

[Table 23]

Microscopic examination of the obtained composite material at or aroundthe interface between the core layer and the surface layer found thepresence of the intermediate layer in which the resin impregnatedsheet-like material was arranged.

Example 14

Except that the surface layer, the intermediate layer and the core layershown in the following TABLE 24 were formed, a composite material wasproduced in the same manner as in Example 13.

It was found that the intermediate layer of a thickness of about 3 mmmade of epoxy resin was formed between the core layer and the surfacelayer.

[Table 24]

Reference Example 1

Except that no intermediate layer was provided, a composite material 1 ihaving a core layer 2 i and a surface layer 3 i as shown in FIG. 14 wasproduced in the same manner as in Example 13.

Reference Example 2

As shown in FIG. 15, a composite material 1 j consisting of only thesurface layer of Example 13 was produced.

The measurements were made of the shear strength of the interfacebetween the core layer and the surface layer of each of the compositematerials obtained from Examples 13, 14 and Reference Examples 1, 2. Theresults are shown in TABLE 25, together with the results of the bendingstrength, bending modulus, compression strength (JIS K 2101) and woodworkability such as cutting.

The shear strength was measured in accordance with the method prescribedby JIS Z 2101 with TENSIRON UCT-5T made of ORIENTEC CO., LTD. at a crosshead velocity of 1 mm/min.

[Table 25]

It will be clearly understood from TABLE 25 that the composite materialhaving the intermediate layer which is provided between the surfacelayer and the core layer and the surface. layer and through which thecore layer are integrally bonded to each other, as the compositematerial of claim 13, can provide a far stronger interfacial strengththan the composite material having no intermediate layer and, further,can fully be applicable to the SEW process as one of a variety of uses.

Example 15

Except that the surface layer, the intermediate layer and the core layershown in the following TABLE 26 were formed, a composite material wasproduced in the same manner as in Example 13.

Used as propylene oxide added polyether polyol was SUMIPHEN 1703(hydroxyl value of 380, polyol equivalent of 147) available fromSumitomo Bayer Urethane Ltd.

The composite material produced was found to have the core layer havingthe shear strength of 6 MPa, the surface layer having the shear strengthof 8 MPa, and the intermediate layer of a thickness of 1 mm formedtherebetween and formed of low-power foam resin having a density of 0.50that is 1.1 times as dense as in the core layer.

[Table 26]

Example 16

Except that the surface layer, the intermediate layer and the core layershown in the following TABLE 27 were formed, a composite material wasproduced in the same manner as in Example 13.

The composite material produced was found to have the core layer havingthe shear strength of 6 MPa, the surface layer having the shear strengthof 8 MPa, and intermediate layer portions of a thickness of 1 mm formedbetween the core layer and the non-woven fabric and between thenon-woven fabric and the surface layer, respectively, and having adensity of 0.50 that is 1.1 times as dense as in the core layer.

[Table 27]

Example 17

Except that the surface layer, the intermediate layer and the core layershown in the following TABLE 28 were formed, a composite material wasproduced in the same manner as in Example 13.

The composite material produced was found to have the core layer havingthe shear strength of 6 MPa, the surface layer having the shear strengthof 8 MPa, and intermediate layer portions of a thickness of 1 mm formedbetween the core layer and the non-woven fabric and between thenon-woven fabric and the surface layer, respectively, and having adensity of 0.48 that is 1.1 times as dense as in the core layer.

[Table 28]

The composite materials obtained in Examples 15-17 and ComparativeExample 5 were subjected to the shearing tests in accordance with themethod prescribed by JIS Z 2101, in accordance with which compressiveforce was applied to the composite material in the direction parallel tothe fiber extending direction in such a manner that a breaking surfacecan be formed in an intermediate layer portion 7 k between a core layer2 k and a surface layer 3 k, as shown in FIG. 16. The measurementresults are shown in TABLE 29. In addition, the measurements were madeof the bending strength and bending modulus in accordance with themethod prescribed by JIS Z 2101, the results being shown in TABLE 29,together with the results of the repeated bending fatigue tests.

It is to be noted that the repeated bending fatigues tests wereperformed in accordance with the fixed stress repeated bending testswith a span distance of 1,960 mm, a bending stress of 60 MPa and afrequency of 6 Hz. Not less than 1×10⁷ in the number of bending repeateduntil breakage is represented by ⊚, Less than 1×10⁷ to not less than1×10⁶ is represented by ∘, and Less than 1×10⁶ is represented by x.Also, as to the destruction, the case of destruction being causedbetween the surface layer and the core layer is represented by x, andthe case of no destruction being found between the surface layer and thecore layer or the case of destruction being not caused by repeatedbending of not less than 1×10⁷ is represented by ∘.

[Table 29]

It will be clearly understood from TABLE 29 that the composite materialof claim 20 provides excellent properties of not only the bendingstrength and the bending modulus but also the durability against therepeated bending.

Capabilities of Exploitation in Industry

The composite material according to the present invention thusconstructed can achieve further improvement of compression strength andnailing property.

When the composite material is used as cross ties and the like, thatwill be able to absorb vibrations easily to reduce noise. In addition,since the core layer is resistant to destroying, if damage originatesfrom deterioration, the damage will then be caused to the surface layerand thus will be easily detectable.

Further, specific gravity of the composite material produced can beeasily adjusted by adjusting the specific gravity of fillers of the corelayer, such that the composite material can be used for various usesranging from weight saving use to weighted use.

With the constitution of claim 5, in particular, the coefficient ofthermal expansion of the core layer comes near that of the surfacelayer. Consequently, even when environmental temperature varies largely,little deformation is produced in an interface between the surface layerand the core layer, thus providing a high reliability of long-termlayer-to-layer adhesion properties.

With the constitution of claim 6, the resistance to the repeatedunnailing is improved, thus producing the result that when the compositematerial is used as cross ties, the time-interval for maintenance of thecross ties can be elongated.

With the constitution of claim 9, destroy of the core layer issuppressed, thus producing improvement in flexibility, as well as inbending strength, compression proportional limit, nailing property andunnailing property. Hence, when the composite material is used as crossties and the like, that will be able to easily absorb vibrations toreduce noise. In addition, since the core layer is resistant todestroying, if damage originates from deterioration, the damage willthen be caused to the surface layer and thus will be easily detectable.

With the constitution of claims 14 and 15, the composite material cansuitably be used for a cross tie (a railway sleeper, in particular), apressure bearing board and a shield-use take-off/accession cofferingwall (SEW) which require high bending strength and bending modulus.Also, since the product size can be reduced for purposes not requiringhigh bending strength and bending modulus, cost reduction of materialcan be achieved. Also, since the intermediate fiber-reinforced layer isprovided between the filler-containing layer and the filler-containinglayer, the nail struck can be bound by the long fibers of theintermediate fiber-reinforced layer to provide an improved nail holdingperformance.

With the constitution of claim 18, destroy of the core layer issuppressed, thus producing improvement in flexibility, as well as inbending strength, compression proportional limit, nailing property andunnailing property. Hence, when the composite material is used as crossties and the like, that will be able to absorb vibrations further easilyto reduce noise.

With the constitution of claim 19, the core layer and the surface layerare integrated through the non-foam thermosetting resin layer, thusproviding a very excellent interfacial strength.

When used as a material used for the SEW construction method which isone of a variety of uses of the same, the composite material can be usedas a unit by itself, without any need for a plurality of flat plates tobe laminated and adhesive bonded together under pressure, differentlyfrom the conventional synthetic wood. Thus, the adhering process can beomitted and the strength can be made equal to or more than that of theconventional synthetic wood.

With the constitution of claim 20, the durability against the repeatedbending fatigue, in particular, can be improved so that the compositematerial can be used further suitably for structural material, such as awall material for the SEW construction method, and a railway sleeperwhich require high durability against the bending fatigue.

With the constitution of claim 21, the intermediate layer can be allowedto have further strength by a high strength sheet and the like beingused as a resin impregnated sheet.

When the intermediate layer is formed, the non-foam thermosetting resinmay be impregnated in the resin-containing sheet-like material, forfacilitation of the forming of the intermediate layer.

With the constitution of claim 22, the composite material of highermechanical strength, capable to form closed cells easily when foamed,and excellent unabsorbent can be produced.

With the constitution of claim 26, a further stable bending strength canbe yielded.

The synthetic cross tie according to claim 27, which uses the compositematerial of the present invention mentioned above for it, have the sameexcellent capabilities as the native wood. It is of excellent inadhesion strength in the interface, in other words, in interfacialstrength.

TABLE 1 Volume Filling % Density Rate Core layer Filler Silica sand: 651.83 0.93 Average particle size: 1.14 mm, (Resin 0.4)  Peak particlesize ratio: 0.07 Bulk density: 1.82 g/cm³ Standard size: 2 mm Passing,80 Volume % 1.4 mm Remaining Standard size: 212 μm Passing. 20 Volume %106 μm Remaining Resin Polyether polyol  (100 parts by weight) PolymericMDI (NCO % = 31%)  (130 parts by weight) Silicone oil foam stabilizer(0.15 parts by weight) Water  (0.5 parts by weight) Dibutyltin lauratecatalyst  (0.5 parts by weight) Surface layer Long fiber E glass fiberroving 20 0.97 — 13 μm mono-filament bundling (Resin 0.58) ResinPolyether polyol  (100 parts by weight) 80 Polymeric MDI (NCO % = 31%) (160 parts by weight) Silicone oil foam stabilizer (0.15 parts byweight) Water  (0.7 parts by weight) Dibutyltin laurate catalyst  (1.8parts by weight)

TABLE 2 Volume Filling % Density Rate Core layer Filler Silica sand: 551.59 0.98 Average particle size: 1.14 mm, (Resin 0.35) Peak particlesize ratio: 0.59 Bulk density: 1.46 g/cm³ Standard size: 1 mm Passing,30 Volume % 850 μm Remaining Standard size: 600 μm Passing. 70 Volume %500 μm Remaining Resin Polyether polyol  (100 parts by weight) 45Polymeric MDI (NCO % = 31%)  (130 parts by weight) Silicone oil foamstabilizer (0.15 parts by weight) Water  (0.5 parts by weight)Dibutyltin laurate catalyst  (0.5 parts by weight) Surface layer Longfiber E glass fiber roving 14 0.74 — 13 μm mono-filament bundling (Resin0.45) Resin Polyether polyol  (100 parts by weight) Polymeric MDI (NCO %= 31%)  (160 parts by weight) Silicone oil foam stabilizer (0.15 partsby weight) Water  (0.7 parts by weight) Dibutyltin laurate catalyst (1.8 parts by weight)

TABLE 3 Volume Filling % Density Rate Core layer Filler Silica sand: 561.72 1.0 Average particle size: 0.6 mm, (Resin 0.55) Standard size: 710μm Passing, 100 Volume % 600 μm Remaining Glass short fiber 1 6 mm inlength Bulk density after mixture: 1.48 g/cm³ Resin Polyether polyol(100 parts by weight) 43 Polymeric MDI (NCO % = 31%)  (60 parts byweight) Silicone oil foam stabilizer  (1 parts by weight) Water  (1parts by weight) Dibutyltin laurate catalyst  (0.3 parts by weight)Surface layer Long fiber E glass fiber roving 12 0.63 — 13 μmmono-filament bundling (Resin 0.37) Resin Polyether polyol (100 parts byweight) 88 Polymeric MDI (NCO % = 31%) (160 parts by weight) Siliconeoil foam stabilizer  (1 parts by weight) Water  (1 parts by weight)Dibutyltin laurate catalyst  (1.8 parts by weight)

TABLE 4 Volume Filling % Density Rate Core layer Filler N Lightavailable from 55 0.70 0.95 NAIGAI CERAMIC CO., LTD. (Resin 0.30)Average particle size: 1.00 mm, Standard size: 1.4 mm Passing, 100Volume % 1 mm Remaining Bulk density: 0.58 g/cm³ Resin Polyether polyol (100 parts by weight) 45 Polymeric MDI (NCO % = 31%)   (60 parts byweight) Silicone oil foam stabilizer (0.15 parts by weight) Water  (0.5parts by weight) Dibutyltin laurate catalyst  (0.5 parts by weight)Surface layer Long fiber E glass fiber roving 14 0.74 — 13 μmmono-filament bundling (Resin 0.45) Resin Polyether polyol  (100 partsby weight) 86 Polymeric MDI (NCO % = 31%)  (160 parts by weight)Silicone oil foam stabilizer (0.15 parts by weight) Water  (0.7 parts byweight) Dibutyltin laurate catalyst  (1.8 parts by weight)

TABLE 5 Volume Filling % Density Rate Core layer Filler Silica sand: 411.77 0.71 Average particle size: 0.6 mm, Standard size: 710 μm Passing,100 Volume % 600 μm Remaining Bulk density: 1.50 g/cm³ Resin Polyetherterephtarate 59 Surface layer Long fiber E glass fiber roving 13 μmmono-filament bundling 24 Resin Unsaturated polyester of iso series (100parts by weight) 57 1.5 — tert-butyl peroxide  (1 parts by weight)(Resin 0.37) Glass Balloon (Specific gravity 0.3)  (6.7 parts by weight)19

TABLE 6 Volume Filling % Density Rate Core layer Filler Silica sand: 270.96 0.5 Average particle size: 0.09 mm, (Resin 0.35) Standard size: 100μm Passing, 100 Volume % 90 μm Remaining Bulk density: 1.41 g/cm³ ResinPolyether polyol  (100 parts by weight) 73 Polymeric MDI (NCO % = 31%) (130 parts by weight) Silicone oil foam stabilizer (0.15 parts byweight) Water  (0.5 parts by weight) Dibutyltin laurate catalyst  (0.3parts by weight) Surface layer Long fiber E glass fiber roving 3 0.4 —13 μm mono-filament bundling (Resin 0.33) Resin Polyether polyol  (100parts by weight) 97 Polymeric MDI (NCO % = 31%)  (160 parts by weight)Silicone oil foam stabilizer (0.15 parts by weight) Water  (0.7 parts byweight) Dibutyltin laurate catalyst  (1.8 parts by weight)

TABLE 7 Volume Filling % Density Rate Core layer Filler Silica sand: 341.12 0.6 Average particle size: 1.14 mm, (Resin 0.35) Peak particle sizeratio: 0.59 Bulk density: 1.46 g/cm³ Standard size: 1 mm Passing, 30Volume % 850 μm Remaining Standard size: 600 μm Passing. 70 Volume % 500μm Remaining Resin Polyether polyol  (100 parts by weight) 66 PolymericMDI (NCO % = 31%)  (130 parts by weight) Silicone oil foam stabilizer(0.15 parts by weight) Water  (0.5 parts by weight) Dibutyltin lauratecatalyst  (0.5 parts by weight) Surface layer Long fiber E glass fiberroving 14 0.74 — 13 μm mono-filament bundling (Resin 0.45) ResinPolyether polyol  (100 parts by weight) 86 Polymeric MDI (NCO % = 31%) (160 parts by weight) Silicone oil foam stabilizer (0.15 parts byweight) Water  (0.7 parts by weight) Dibutyltin laurate catalyst  (1.8parts by weight)

TABLE 8 Volume Filling % Density Rate Core layer Filler Silica sand:(100 parts by weight) 45 1.04 0.62 Average particle size: 0.15 mm (Resin0.24) Glass foam (225 parts by weight) Average particle size: 6 mm Bulkdensity in the mixed state: 1.48 g/cm³ Resin Polyether polyol (100 partsby weight) 55 Polymeric MDI (NCO % = 31%) (170 parts by weight) Siliconeoil foam stabilizer  (1 parts by weight) Water  (1 parts by weight)Dibutyltin laurate catalyst  (0.3 parts by weight) Surface layer Longfiber E glass fiber roving 18 13 μm mono-filament bundling ResinPolyether polyol (100 parts by weight) 82 0.74 — Polymeric MDI (NCO % =31%) (160 parts by weight) (Resin 0.45) Silicone oil foam stabilizer  (1parts by weight) Water  (1 parts by weight) Dibutyltin laurate catalyst (0.5 parts by weight)

TABLE 9 Volume Filling % Density Rate Core layer Filler Silica sand:(100 parts by weight) 45 1.04 0.62 Average particle size: 0.15 mm (Resin0.24) Glass foam (225 parts by weight) Average particle size: 6 mm Bulkdensity in the mixed state: 1.48 g/cm³ Resin Polyether polyol (100 partsby weight) 55 Polymeric MDI (NCO % = 31%)  (30 parts by weight) Siliconeoil foam stabilizer  (1 parts by weight) Water  (1 parts by weight)Dibutyltin laurate catalyst  (0.3 parts by weight) Surface layer Longfiber E glass fiber roving 18 13 μm mono-filament bundling ResinPolyether polyol (100 parts by weight) 82 0.74 — Polymeric MDI (NCO % =31%) (120 parts by weight) (Resin 0.45) Silicone oil foam stabilizer  (1parts by weight) Water  (1 parts by weight) Dibutyltin laurate catalyst (0.5 parts by weight)

TABLE 10 Bending Compression modulus of Bending Bending proportionalUnnailing Repeated surface layer strength modulus limit Nailingperformance unnailing Deflection Ex. 1 12,000 MPa  150 MPa 13,000 MPa 15 MPa ∘ ⊚⊚ ⊚ 1.3% 2 8,800 MPa 130 MPa 8,600 MPa 12 MPa ∘ ⊚⊚ ⊚ 1.7% 37,100 MPa 120 MPa 7,100 MPa 13 MPa ∘ ⊚ ∘ 2.2% 4 8,800 MPa 110 MPa 8,400MPa 12 MPa ∘ ∘ — 1.1% 5 9,000 MPa 100 MPa 8,500 MPa 14 MPa ∘ ∘ — —Compa. Ex. 1 3,000 MPa  20 MPa —  2 MPa ∘ x x — 2 —  90 MPa — 13 MPa x xx — 3 —  40 MPa 6,800 MPa  3 MPa x x — 0.6% 4 —  30 MPa 6,300 MPa  2 MPa∘ x — 0.5%

TABLE 11 Vol. Wt. Filling % % Density Rate Core layer Filler No. 1Silica sand 50 85 1.53 0.92 Particle size: 1.5 mm, (Resin 0.45) Bulkdensity: 1.42 g/cm³ Available from Rokuroya Kogyo Co., Ltd.   (43 partsby weight) Resin Polydiphenylmethane diisocyanate  (140 parts by weight)50 15 Propylene oxide added polyether polyol  (100 parts by weight)Silicone oil foam stabilizer   (1 parts by weight) Water  (0.5 parts byweight) Dibutyltin laurate catalyst  (0.5 parts by weight) Surface layerLong fiber E glass fiber roving 15 — 0.73 — 12 μm mono-filament bundling(200 × 60) Resin Polyether polyol (OH value = 480)  (100 parts byweight) 85 — Polymethylene polyphenyl polyisocyanate  (160 parts byweight) (NCO % = 31%) Silicone oil foam stabilizer (0.15 parts byweight) Water  (0.7 parts by weight) Dibutyltin laurate catalyst  (1.8parts by weight)

TABLE 12 Vol. Wt. Filling % % Density Rate Core layer Filler No. 3Silica sand  (100 parts by weight) 65 91 1.85 0.99 (Available fromRokuroya Kogyo Co., Ltd.) (Resin 0.45) No. 7 Silica sand   (20 parts byweight) (Available from Rokuroya Kogyo Co., Ltd.) Short glass fibermono-filament  (0.4 parts by weight) Diameter: φ 12 μm/Length: 3 mm Bulkdensity in the mixed state: 1.72 g/cm³ Resin Polydiphenylmethanediisocyanate   (74 parts by weight) 35  9 Propylene oxide addedpolyether polyol  (100 parts by weight) Silicone oil foam stabilizer  (1 parts by weight) Water   (1 parts by weight) Dibutyltin lauratecatalyst  (0.3 parts by weight) Surface layer Long fiber E glass fiberroving 15 — 0.73 — 12 μm mono-filament bundling (200 × 60) ResinPolyether polyol (OH value = 480)  (100 parts by weight) 85 —Polymethylene polyphenyl polyisocyanate  (160 parts by weight) (NCO % =31%) Silicone oil foam stabilizer (0.15 parts by weight) Water  (0.7parts by weight) Dibutyltin laurate catalyst  (1.8 parts by weight)

TABLE 13 Vol. Wt. Filling % % Density rate Core Filler No. 3 Silica sand35 92 1.17 0.64 layer Bulk density: 1.42 g/cm³ (Resin Avaliable fromRokuroya Kogya Co., Ltd. 0.4)  (43 parts by weight) ResinPolydiphenylmethane diisocyanate 65 8 (140 parts by weight) Propyleneoxide added polyether polyol (100 parts by weight) Silicone oil foamstabilizer (1 parts by weight) Water (1 parts by weight) Dibutyltinlaurate catalyst (0.5 parts by weight) Surface Long E glass fiber roving0.73 — layer fiber 12 μm mono-filament bundling (200 × 60) 15 ResinPolyether polyol(OH value = 480) (100 parts by weight) Polymethylenepolyphenyl polyisocyanate (NCO% = 31%) 85 (160 parts by weight) Siliconeoil foam stabilizer (0.15 parts by weight) Water (0.7 parts by weight)Dibutyltin laurate catalyst (1.8 parts by weight)

TABLE 14 Compression Bending modulus Bending Bending proportionalUnnailing in the increase of Strength modulus limit performanceDeflection deflection Ex. 6 140 MPa 9,900 MPa  13 MPa ⊚ 0.52% 1,370 MPa7 150 MPa 10,000 MPa   16 MPa ⊚ 0.25% 2,100 MPa Compara. 5  70 MPa 6,000MPa 0.4 MPa x 0.84% 1,660 MPa Ex. 6 — — 8.7 MPa ⊚ — —

TABLE 15 Bending Unnailing strength Bending modulus performanceDeflection Example 6 140 MPa 9,900 MPa ⊚ 0.52% Example 8 160 MPa 9,900MPa ⊚ 0.62% Example 9 150 MPa 9,700 MPa ⊚⊚⊚ 0.56%

TABLE 16 Layer Vol. Volume % Density Ratio Core layer A sheet-likeporous material produced by extruding foal — 0.95 66 vinyl chlorideresin in which 0.05 parts by weight of ADCA was compounded in 100 partsby weight of PVC compound available from Tokuyama Sekisui Co., Ltd.Surface Long E glass fiber roving 0.74 34 layer fiber 9 μm mono-filamentbundling (200 × 60) 14 Resin Polymeric MDI (120 parts by weight)Propylene oxide added polyether polyol 86 (100 parts by weight) Siliconeoil foam stabilizer (1 parts by weight) Water (1 parts by weight)Dibutyltin laurate catalyst (0.5 parts by weight) Void volume about 0.6

TABLE 17 Layer Vol. Volume % Density Ratio Core A sheet-like materialproduced by foaming polyurethane — 0.82 43 layer resin raw material inlow density in which 150 parts by weight of wollastonite is added to 100parts by weight of MDI, polyol available from Sumitomo Bayer UrethaneCo., Ltd. Surface Long E glass fiber roving 0.74 57 layer fiber 9 μmmono-filament bundling (200 × 60) 14 Resin Polymeric MDI (120 parts byweight) Propylene ozide added polyether polyol 86 (100 parts by weight)Silicone oil foam stabilizer (1 parts by weight) Water (1 parts byweight) Dibutyltin laurate catalyst (0.5 parts by weight) Void volumeabout 0.6

TABLE 18 Layer Vol. Volume % Density Ratio Core A sheet-like materialproduced by foaming polyurethane — 0.82 43 layer resin raw material inlow density in which 300 parts by weight of silica sand and powdered PVCis added to 100 parts by weight of MDI, polyol available from SumitomoBayer Urethane Co., Ltd. Surface Long E glass fiber roving 0.74 57 layerfiber 9 μm mono-filament bundling (200 × 60) 14 Resin Polymeric MDI (120parts by weight) Propylene oxide added polyether polyol 86 (100 parts byweight) Silicone oil foam stabilizer (1 parts by weight) Water (1 partsby weight) Dibutyltin laurate catalyst (0.5 parts by weight) Void volumeabout 0.6

TABLE 19 Vol. Den- % sity Core A sheet-like material produced by the —0.5 layer process that after a mixture of 20 parts by weight ofresol-base phenol particles (BERU PAARU available from KANEBO, LTD.) and80 parts by weight of No. 5 silica sand was preheated, the mixture washot-pressed at 200° C. with 20 kgf/cm³ to be molten and was allowed toreact and solidified Surface Long E glass fiber roving 0.74 layer fiber9 μm mono-filament bundling (200 × 60) 14 Resin Polymeric MDI (120 partsby weight) Propylene oxide added polyether polyol 86 (100 parts byweight) Silicone oil foam stabilizer (1 parts by weight) Water (1 partsby weight) Dibutyltin laurate catalyst (0.5 parts by weight) Void volumeabout 0.6

TABLE 20 Vol. Den- % sity Core A polystyrene low power foam produced —0.6 layer by polystyrene (available from SUMITOMO CHEMICAL CO., LTD.)being extruded and foamed. Surface Long E glass fiber roving 0.74 layerfiber 9 μm mono-filament bundling (200 × 60) 14 Resin Polymeric MDI (120parts by weight) Propylene oxide added polyether polyol 86 (100 parts byweight) Silicone oil foam stabilizer (1 parts by weight) Water (1 partsby weight) Dibutyltin laurate catalyst (0.5 parts by weight) Void volumeabout 0.6

TABLE 21 Vol. Den- % sity Core A plate-like elastic urethane foam using— 0.7 layer polyol of low elasticity-use, instead of urethane resin usedfor the surface layer, to adjust the elastic modulus to 100 Mpa SurfaceLong E glass fiber roving 0.74 layer fiber 9 μm mono-filament bundling(200 × 60) 14 Resin Polymeric MDI (120 parts by weight) Propylene oxideadded polyether polyol 86 (100 parts by weight) Silicone oil foamstabilizer (1 parts by weight) Water (1 parts by weight) Dibutyltinlaurate catalyst (0.5 parts by weight) Void volume about 0.6

TABLE 22 Examples Comparative Examples Evaluation Unit 10 11 12 7 8 9 10method Core Ca MPa 350 480 520 — 800 150 100 JIS Z 2101 layer CSa —0.010 0.015 0.008 — 0.003 0.008 0.01 or — more Ea MPa 70 140 250 — 450150 25 JIS Z 2101 ESa — 0.020 0.020 0.012 — 0.003 0.006 1.0 or — moreDBa MPa 5.2 6.8 9.9 — 5.0 2.5 6.1 — Surface Ca MPa 300 300 300 300 300300 300 JIS Z 2101 layer CSa — 0.012 0.012 0.012 0.012 0.012 0.012 0.012— Ea MPa 900 900 900 900 900 900 900 JIS Z 2101 ESa — 0.02 0.02 0.020.02 0.02 0.02 0.02 — Bending strength MPa 102 110 124 104 68 60 52 JISZ 2101 Nailing performance — ∘ ∘ ∘ ∘ ∘ ∘ x — Unnailing — ∘ ∘ ∘ ∘ ∘ x ∘ —performance

TABLE 23 Vol. % Density Core layer Filler No. 3 Silica sand 55 1.63Particle size: 1.5 mm Bulk density: 1.4 g/cm³ True density: 1.4 g/cm³ 0.Resin Polymeric MDI (120 parts by weight) Propylene oxide addedpolyether polyol 45 (Hydroxyl value: 380, Polyol equivalent: 147) (100parts by weight) Silicone oil foam stabilizer (0.7 parts by weight)Water (1.8 parts by weight) Dibutyltin laurate catalyst (0.15 parts byweight) Surface layer Long E glass fiber roving 15 0.73 fiber 12 μmmono-filament bundling (200 × 60) Resin Polymeric MDI (NCO = 31%) (160parts by weight) Polyether polyol (Hydroxyl value: 480) (100 parts byweight) Silicone oil foam stabilizer (0.7 parts by weight) 85 Water (1.8parts by weight) Dibutyltin laurate catalyst (0.15 parts by weight)Intermediate A resin impregnated sheet-like material layer (Polyesternon-woven fabric (SUPAN BONDO E 1050 available from ASAHI CHEMICALINDUSTRIAL CO., LTD.) Resin Polyether polyol(Hydroxyl value: 480) (100parts by weight) Polymeric MDI (NCO = 31%) (160 parts by weight)Silicone oil foam stabilizer (0.7 parts by weight) Dibutyltin lauratecatalyst (0.15 parts by weight)

TABLE 24 Vol. % Density Core layer Filler No. 3 Silica sand 55 1.63Particle size: 1.5 mm Bulk density: 1.4 g/cm³ True density: 1.4 g/cm³ 0.Resin Polymeric MDI (120 parts by weight) Propylene oxide addedpolyether polyol 45 (Hydroxyl value: 380, Polyol equivalent: 147) (100parts by weight) Silicone oil foam stabilizer (0.7 parts by weight)Water (1.8 parts by weight) Dibutyltin laurate catalyst (0.15 parts byweight) Surface layer Long E glass fiber roving 15 0.73 fiber 12 μmmono-filament bundling (200 × 60) Resin Polymeric MDI (NCO = 31%) (160parts by weight) Polyether polyol (Hydroxyl value: 480) (100 parts byweight) Silicone oil foam stabilizer (0.7 parts by weight) 85 Water (1.8parts by weight) Dibutyltin laurate catalyst (0.15 parts by weight)Intermediate A resin impregnated sheet-like material layer (Glass cloth(MICRO GLASS CLOTH YEG4501 available from Nippon Sheet Glass Co., Ltd.)Resin Epoxy resin (ESUDAIN 400 available from Sekisui Chemical Co.,Ltd.)

TABLE 25 Example Example Reference Reference 13 14 Example 1 Example 2Shear strength (MPa) 12 13 6 9 Bending strength (MPa) 140 130 90 120Bending modulus (GPa) 10 9 7 8 Compression strength 100 102 101 60 (MPa)Wood workability ∘ ∘ x ∘

TABLE 26 Vol. Wt. Den- Filling % % sity rate Core layer Filler No. 7Silica sand 1.42 0.93 (particle size: 0.15 mm) (100 parts by weight)(Resin Expanded shale 65 88 0.45) (particle size: 3 mm) (220 parts byweight) Bulk density in the mixed state (1.36 g/cm³) Resin Polymeric MDI(140 parts by weight) Propylene oxide added polyether polyol 35 12 (100parts by weight) Silicone oil foam stabilizer (1 parts by weight) Water(1 parts by weight) Dibutyltin laurate catalyst (0.5 parts by weight)Surface Long E glass fiber roving 0.74 — layer fiber 9 μm mono-filamentbundling (200 × 60) 14 Resin Polymeric MDI (120 parts by weight)Propylene oxide added polyether polyol 86 (100 parts by weight) Siliconeoil foam stabilizer (1 parts by weight) Water (1 parts by weight)Dibutyltin laurate catalyst (0.5 parts by weight) Intermediate ResinPolymeric MDI (99 parts by weight) layer Propylene oxide added polyetherpolyol (100 parts by weight) Silicone oil foam stabilizer (1 parts byweight) Water (0.1 parts by weight) Dibutyltin laurate catalyst (0.5parts by weight)

TABLE 27 Vol. Wt. Den- Filling % % sity rate Core layer Filler No. 7Silica sand 1.42 0.93 (particle size: 0.15 mm) (100 parts by weight)(Resin Expanded shale 65 88 0.45) (particle size: 3 mm) (220 parts byweight) Bulk density in the mixed state (1.36 g/cm³) Resin Polymeric MDI(140 parts by weight) Propylene oxide added polyether polyol 35 12 (100parts by weight) Silicone oil foam stabilizer Water (1 parts by weight)Dibutyltin laurate catalyst (0.5 parts by weight) Surface Long E glassfiber roving 14 0.74 — layer fiber 9 μm mono-filament bundling (200 ×60) Resin Polymeric MDI (120 parts by weight) Propylene oxide addedpolyether polyol 86 (100 parts by weight) Silicone oil foam stabilizer(1 parts by weight) Water (1 parts by weight) Dibutyltin lauratecatalyst (0.5 parts by weight) A resin impregnated sheet-like material(Polyester non-woven fabric (SUPAN BONDO E 1050 available from ASAHICHEMICAL INDUSTRIAL CO., LTD.) Intermediate Resin Polymeric MDI (99parts by weight) layer Propylene oxide added polyether polyol (100 partsby weight) Silicone oil foam stabilizer (1 parts by weight) Water (0.1parts by weight) Dibutyltin laurate catalyst (0.5 parts by weight)

TABLE 28 Vol. Wt. Den- Filling % % sity rate Core layer Filler No. 7Silica sand 1.42 0.93 (particle size: 0.15 mm) (100 parts by weight)(Resin Expanded shale 65 88 0.45) (particle size: 3 mm) (220 parts byweight) Bulk density in the mixed state (1.36 g/cm³) Resin Polymeric MDI(140 parts by weight) Propylene oxide added polyether polyol 35 12 (100parts by weight) Silicone oil foam stabilizer Water (1 parts by weight)Dibutyltin laurate catalyst (0.5 parts by weight) Surface Long E glassfiber roving 0.74 — layer fiber 9 μm mono-filament bundling (200 × 60)14 Resin Polymeric MDI (120 parts by weight) Propylene oxide addedpolyether polyol 86 (100 parts by weight) Silicone oil foam stabilizer(1 parts by weight) Water (1 parts by weight) Dibutyltin lauratecatalyst (0.5 parts by weight) A resin impregnated sheet-like material(vinylon non-woven fabric (SPUN LACE available from KURARAY CO., LTD.,Weight: 55 g/cm²) Intermediate Resin Polymeric MDI (99 parts by weight)layer Propylene oxide added polyether polyol (100 parts by weight)Silicone oil foam stabilizer (1 parts by weight) Water (0.1 parts byweight) Dibutyltin laurate catalyst (0.5 parts by weight)

TABLE 29 Comparative Example 15 Example 16 Example 17 Example 5 Shearstrength (MPa) (7.6) 7.8 7 5.2 Destruction Destruction of Destruction ofDestruction of Destruction of conformation matrix of core layerinterface interface interface Bending strength (MPa) 135 135 135 70Bending modulus (MPa) 9,700 9,800 9,800 6,000 Durability against ∘ ⊚ ∘ xrepeated bending Destruction caused by ∘ ∘ ∘ x repeated bending

What is claimed is:
 1. A composite material comprising: a core layercomprising a particulate filler having an average particle size of 0.5mm or more and synthetic resin and containing the filler having a weight0.7 times or more the product of volume of the core layer and bulkdensity of the filler; and a surface layer comprising a thermosettingresin reinforced by long fibers extending parallel in a longitudinaldirection thereof, said long fibers being present in an amount of 5volume % to 40 volume %; and the surface layer being laminated on thecore layer to cover at least one surface of the core layer with respectto a thickness direction thereof.
 2. The composite material according toclaim 1, wherein the surface layer has a density of 0.3 g/cm³ or more to1.5 g/cm³ or less.
 3. The composite material according to claim 1, whichcomprises the surface layer having a bending modulus of 6,000 MPa ormore and a bending strength of 100 MPa or more.
 4. The compositematerial according to claim 1, wherein the filler has two or more peakareas that constitute 8 volume % or more on a particle size distributioncurve plotting particle size in abscissa and a volume ratio of fillerper particle size to all fillers in ordinate and also has the sizedistribution that most frequent particle size values in the smaller peakarea of 8 volume % or more is 0.7 or less of most frequent particle sizevalues in the larger peak area of 8, volume % or more next to thesmaller peak area.
 5. The composite material according to claim 1,wherein the synthetic resin forming the core layer is thermosettingresin.
 6. The composite material according to claim 1, wherein thesynthetic resin forming the core layer is thermoplastic resin.
 7. Thecomposite material according to claim 1, wherein the synthetic resinforming the core layer is thermosetting polyurethane resin foam ofpolyol equivalent of 230 or more to 1,500 or less or thermosettingpolyurethane resin foam having a density of 0.3 g/cm³ or more and polyolequivalent of 1,500 or less.
 8. The composite material according toclaim 1, wherein the core layer is formed by a plurality of core layerforming composition layers.
 9. The composite material according to claim8, wherein one of the core layer forming composition layers isthermosetting resin reinforced by long fibers extending parallel in alongitudinal direction thereof or thermosetting resin includinglightweight filler reinforced by long fibers extending parallel in alongitudinal direction thereof.
 10. The composite material according toclaim 1, wherein the core layer has a compression shear strength DBa of5 MPa or more.
 11. The composite material according to claim 1, whereinthe core layer and the surface layer are integrally adhesive bonded toeach other through an intermediate layer comprising non-foamthermosetting resin or low-power foam resin.
 12. The composite materialaccording to claim 11, wherein an intermediate layer portion has thecompression shear strength of 6 MPa or more, or the surface layer andthe core layer both have the compression shear strength of 6 MPa ormore, when compressive force is applied to the composite material in adirection parallel to the fiber extending direction of the long fibersof the surface layer so that a breaking surface can be formed in theintermediate layer portion, and wherein the composite material has thephysical property that either the surface layer or the core layer isfirst broken when the compressive force is applied to the compositematerial in the direction parallel to the fiber extending direction ofthe long fibers of the surface layer so that the breaking surface can beformed in the intermediate layer portion.
 13. The composite materialaccording to claim 11, wherein a resin-impregnated sheet-like materialis arranged in the intermediate layer.
 14. The composite materialaccording to claim 1, wherein the synthetic resin of the core layer ispolyurethane resin foam and the resin of the surface layer ispolyurethane resin foam.
 15. The composite material according to claim1, which has a total thickness of 100 mm or more and a ratio between athickness of the core layer and a sum total of thickness of the surfacelayer covering the core layer in the thickness direction is within therange of 9/1 to 1/1.
 16. The composite material according to claim 9,wherein the core layer has at least two core layer forming compositionlayers (A) comprising filler and synthetic resin and at least one corelayer forming composition layer (B) comprising thermosetting resinreinforced by long fibers interposed between two core layer formingcompositions (A),(A) of the at least two core layer forming compositionlayers (A) and extending parallel in a longitudinal direction of thecomposite material, and wherein a ratio between a sum total of thicknessof the core layer forming composition layer (A) and a sum total ofthickness of the core layer forming composition layer (B) is within therange of 95/5 to 50/50.
 17. The composite material according to claim 1,wherein the surface layer is laminated on the core layer to cover atleast two surfaces of the corer layer with respect to a thicknessdirection thereof; the composite material has a total thickness of 100mm or more with respect to a thickness direction thereof; and athickness of the surface layer on the side thereof on which a pullingforce is exerted when the composite material is bent in the thicknessdirection is 5% or more to 25% or less of the total thickness and thethickness of the surface layer on the side thereof on which acompressive force is exerted is 1.5% or more to 15% or less of the totalthickness.
 18. The composite material according to claim 1, wherein thesurface layer surrounds four surfaces of the core layer and constitutes10 volume % or more to 65 volume % or less of the total of the compositematerial.
 19. A synthetic cross tie comprising a composite materialaccording to claim
 1. 20. The composite material according to claim 12,wherein a resin-impregnated sheet-like material is arranged in theintermediate layer.
 21. The composite material according to claim 18,wherein the core layer has at least two core layer forming compositionlayers (A) comprising filler and synthetic resin and at least one corelayer forming composition layer (B) comprising thermosetting resinreinforced by long fibers interposed between two core layer formingcompositions (A),(A) of the at least two core layer forming compositionlayers (A) and extending parallel in a longitudinal direction of thecomposite material, and wherein a ratio between a sum total of thicknessof the core layer forming composition layer (A) and a sum total ofthickness of the core layer forming composition layer (B) is within therange of 95/5 to 50/50.
 22. A composite material comprising: a corelayer comprising a particulate filler having an average particle size of0.5 mm or more and synthetic resin and containing the filler having aweight 0.7 times or more the product of volume of the core layer andbulk density of the filler; and a surface layer comprising athermosetting resin including lightweight filler reinforced by longfibers extending parallel in a longitudinal direction thereof, said longfibers being present in an amount of 5 volume % to 40 volume %; and thesurface layer being laminated on the core layer to cover at least onesurface of the core layer with respect to a thickness direction thereof.23. The composite material according to claim 22, wherein the surfacelayer has a density of 0.3 g/cm³ or more to 1.5 g/cm³ or less.
 24. Acomposite material comprising a core layer comprising filler andsynthetic resin and a surface layer comprising synthetic resin foam andlaminated on the core layer to cover at least one surface of the corelayer with respect to a thickness direction thereof, wherein a variationcurve of bending stress of the core layer that varies with the bendingand deflection has a singular point at which slope of the tangent linedecreasing gradually from the point in time at which the bending isstarted increases again before becoming negative.
 25. The compositematerial according to claim 24, wherein the synthetic resin foam isthermosetting resin foam reinforced by long fibers extending parallel ina longitudinal direction thereof.
 26. The composite material accordingto claim 24, wherein the core layer has deflection of 0.8% or less atthe singular point.
 27. The composite material according to claim 24,wherein the core layer has the bending modulus of 800 MPa or more whenfurther deflected from deflection at the singular point.
 28. Thecomposite material according to claim 25, wherein the core layer hasdeflection of 0.8% or less at the singular point.
 29. A compositematerial comprising a core layer comprising synthetic resin as a maincomponent and a surface layer comprising foam thermosetting resinreinforced by long fibers extending parallel in a longitudinal directionthereof or elastic synthetic resin reinforced by long fibers extendingparallel in a longitudinal direction thereof and laminated on the corelayer to cover both surfaces of the core layer with respect to athickness direction thereof, wherein the core layer and the surfacelayer have the relation that satisfies the equations of CSa≧½×CSb,Ea<Eb, and ESa≧½×ESb (where CSa represents yield strain in compressionof the core layer; CSb represents yield strain in compression of thesurface layer; Ea represents a tension elasticity modulus of the corelayer; Eb represents a tension elasticity modulus of the surface layer;ESa represents yield strain in tension of the core layer; and ESbrepresents yield strain in tension of the surface layer).
 30. Thecomposite material according to claim 29, wherein it follows that0.005≦CSa, 50 MPa≦Ea, 0.005≦ESa, 0.01≦CSb, 5,000 MPa≦Eb≦18,000 MPa, and0.01≦ESb.